The human nasal response to capsaicin

Capsicum annuum L. and its bioactive constituents: A critical review of a traditional culinary spice in terms of its modern pharmacological potentials with toxicological issues

Capsicum annuum L., commonly known as chili pepper, is used as an important spice globally and as a crude drug in many traditional medicine systems. The fruits of C. annuum have been used as a tonic, antiseptic, and stimulating agent, to treat dyspepsia, appetites, and flatulence, and to improve digestion and circulation. The article aims to critically review the phytochemical and pharmacological properties of C. annuum and its major compounds. Capsaicin, dihydrocapsaicin, and some carotenoids are reported as the major active compounds with several pharmacological potentials especially as anticancer and cardioprotectant. The anticancer effect of capsaicinoids is mainly mediated through mechanisms involving the interaction of Ca²⁺ -dependent activation of the MAPK pathway, suppression of NOX-dependent reactive oxygen species generation, and p53-mediated activation of mitochondrial apoptosis in cancer cells. Similarly, the cardioprotective effects of capsaicinoids are mediated through their interaction with cellular transient receptor potential vanilloid 1 channel, and restoration of calcitonin gene-related peptide via Ca²⁺ -dependent release of neuropeptides and suppression of bradykinin. In conclusion, this comprehensive review presents detailed information about the traditional uses, phytochemistry, and pharmacology of major bioactive principles of C. annuum with special emphasis on anticancer, cardioprotective effects, and plausible toxic adversities along with food safety.

Prevalence, comorbidities, diagnosis, and treatment of nonallergic rhinitis: real-world comparison with allergic rhinitis

Rhinitis is among the most common respiratory diseases in children. Nonallergic rhinitis, which involves nasal symptoms without evidence of systemic allergic inflammation or infection, is a heterogeneous entity with diverse manifestations and intensities. Nonallergic rhinitis accounts for 16%-89% of the chronic rhinitis cases, affecting 1%-50% (median 10%) of the total pediatric population. The clinical course of nonallergic rhinitis is generally rather mild and less likely to be associated with allergic comorbidities than allergic rhinitis. Here, we aimed to estimate the rate of coexisting comorbidities of nonallergic rhinitis. Nonallergic rhinitis is more prevalent during the first 2 years of life; however, its underestimation for children with atopic tendencies is likely due to low positive rates of specific allergic tests during early childhood. Local allergic rhinitis is a recently noted phenotype with rates similar to those in adults (median, 44%; range, 4%-67%), among patients previously diagnosed with nonallergic rhinitis. Idiopathic rhinitis, a subtype of nonallergic rhinitis, has been poorly studied in children, and its rates are known to be lower than those in adults. The prevalence of nonallergic rhinitis with eosinophilia syndrome is even lower. A correlation between nonallergic rhinitis and pollution has been suggested owing to the recent increase in nonallergic rhinitis rates in highly developing regions such as some Asian countries, but many aspects remain unknown. Conventional treatments include antihistamines, intranasal corticosteroids, and recent treatments include combination of intranasal corticosteroids with azelastin or decongestants. Here we review the prevalence, diagnosis, comorbidities, and treatment recommendations for nonallergic rhinitis versus allergic rhinitis in children.

Topical capsaicin versus topical ibuprofen in acute musculoskeletal injuries: A randomized, double-blind trial

Background:

Acute musculoskeletal pain is one of the common causes of emergency admissions. Topical analgesics are an easily tolerated option in the treatment of these pains.

Objective:

This study aimed to compare the efficacy of topical capsaicin and topical non-steroidal anti-inflammatory drugs in acute musculoskeletal injuries.

Methods:

In this prospective, randomized, controlled, double-blinded study, patients were allocated to two groups—the topical non-steroidal anti-inflammatory drug (n = 60) and topical capsaicin (n = 59). For both groups, the first dose treatment was applied as a thin layer in the emergency department to a maximum area of 5 × 5 cm. The remaining doses were administered at home by the patients for 72 h. The initial visual analog scale scores were compared with the 60th and 120th minute as well as the 24th and 72nd hour values. Differences between the visual analog scale scores, clinical response to the treatment, and side effects were evaluated.

Results:

The proportional reduction in visual analog scale scores for topical capsaicin was significantly higher, especially at 36 and 72 h. These rates were 0.75 (95% confidence interval: 0.77–1.42; p = 0.029) and 9.08 (95% confidence interval: 1.02–17.14; p = 0.028) at 36 h, respectively. At 72 h, they were 1.27 (95% confidence interval: 0.48–2.05; p = 0.002) and 17.07 (95% confidence interval: 8.39–25.76; p < 0.001), respectively. In the topical capsaicin group, the clinical response to treatment was significantly higher (p = 0.001). Treatment-related systemic side effects were experienced only in the topical non-steroidal anti-inflammatory drug group (1.7%).

Conclusion:

Topical capsaicin can be used safely in patients presenting to the emergency department with acute pain with its high analgesic efficacy and absence of systemic side effects.

Impact of capsaicin on aroma release: in vitro and in vivo analysis

Capsaicin is the main bioactive compound in chili pepper that leads to the perception of "spiciness". However, the effect of capsaicin on aroma release in the nose remains unexplained. This is the first study designed to measure capsaicin's impact on aroma release during consumption. In vitro studies, using static headspace analysis by atmospheric pressure chemical ionization-mass spectrometry (APCI-MS), showed no impact of capsaicin (5 ppm) on the gas-liquid partitioning equilibria of a range of aroma compounds. However, a significant reduction in aroma release was observed in vivo, during oral melting of a model ice cube system (p < 0.05) included 5 ppm capsaicin. The total release of aroma into the nasal cavity was decreased, such that only 49% of 3-methylbutanal, 60% of 1-octen-3-ol and 83% of linalool was released. This is the first evidence of capsaicin's reduction effect on aroma release during consumption. It was also found that 5 ppm capsaicin increased saliva secretion by 75%, which may have led to the dilution of aroma compounds in the mouth and directly impacted the aroma release into the nasal cavity. The most hydrophilic compound (3-methylbutanal) was affected by capsaicin to a greater extent than the hydrophobic compound (linalool), the solvent effect of the additional saliva may explain this.

Characterization of tear production in subjects with dry eye disease during intranasal tear neurostimulation: Results from two pivotal clinical trials

PURPOSE

The intranasal tear neurostimulator (ITN) activates the nasolacrimal pathway, which is involved with basal and bolus tear secretion. These studies characterized the acute and long-term effectiveness of the ITN in stimulating tear production in subjects with dry eye disease (DED).

METHODS

Study 1: Randomized, double-masked, dual-controlled, 1-day crossover. Study 2: Single-arm, open-label, 180-day prospective cohort. Eligible subjects had basal unstimulated Schirmer test (with anesthesia) ≤10 mm and intranasal cotton swab-stimulated Schirmer test at least 7 mm greater in the same eye, and Ocular Surface Disease Index^® ≥13 and ≥ 23, in Studies 1 and 2, respectively. Study 1: Subjects (n = 48) received three randomized test applications: active intranasal, extranasal (active control), and sham intranasal (inactive control) stimulation, 3 min/application with 1-hour minimum between applications. Primary outcome measure was the difference in Schirmer test scores during active intranasal and control applications. Study 2: Subjects (n = 97) performed intranasal neurostimulation for ≤3 min/application, 2-10 times/day. Primary outcome measure was the difference in Schirmer scores (stimulated minus unstimulated) at day 180. Both studies recorded device-related adverse events (AEs).

RESULTS

Study 1: Schirmer scores (mean ± SEM) were significantly greater (p < 0.0001) with active intranasal (25.3 ± 1.5 mm) vs extranasal (9.5 ± 1.2 mm) and sham (9.2 ± 1.1 mm) applications. Study 2: Schirmer scores were significantly greater (p < 0.0001) with ITN stimulation vs unstimulated at day 180 (17.3 ± 1.3 mm vs 7.9 ± 0.7 mm). No serious device-related AEs were reported in either study.

CONCLUSION

The ITN was well-tolerated and effective in stimulating tear production with acute and long-term use in DED. CLINICALTRIALS.

GOV IDENTIFIER

NCT02680158 and NCT02526290.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Biological Activities of Red Pepper (Capsicum annuum) and Its Pungent Principle Capsaicin: A Review

Capsaicin, the pungent alkaloid of red pepper (Capsicum annuum) has been extensively studied for its biological effects which are of pharmacological relevance. These include: cardio protective influence, antilithogenic effect, antiinflammatory, and analgesia, thermogenic influence, and beneficial effects on gastrointestinal system. Therefore, capsaicinoids may have the potential clinical value for pain relief, cancer prevention and weight loss. It has been shown that capsaicinoids are potential agonists of capsaicin receptor (TRPV1). They could exert the effects not only through the receptor-dependent pathway but also through the receptor-independent one. The involvement of neuropeptide Substance P, serotonin, and somatostatin in the pharmacological actions of capsaicin has been extensively investigated. Topical application of capsaicin is proved to alleviate pain in arthritis, postoperative neuralgia, diabetic neuropathy, psoriasis, etc. Toxicological studies on capsaicin administered by different routes are documented. Capsaicin inhibits acid secretion, stimulates alkali and mucus secretion and particularly gastric mucosal blood flow which helps in prevention and healing of gastric ulcers. Antioxidant and antiinflammatory properties of capsaicin are established in a number of studies. Chemopreventive potential of capsaicin is evidenced in cell line studies. The health beneficial hypocholesterolemic influence of capsaicin besides being cardio protective has other implications, viz., prevention of cholesterol gallstones and protection of the structural integrity of erythrocytes under conditions of hypercholesterolemia. Beneficial influences of capsaicin on gastrointestinal system include digestive stimulant action and modulation of intestinal ultrastructure so as to enhance permeability to micronutrients.

Cough reflex sensitization from esophagus and nose

The diseases of the esophagus and nose are among the major factors contributing to chronic cough although their role in different patient populations is debated. Studies in animal models and in humans show that afferent C-fiber activators applied on esophageal or nasal mucosa do not initiate cough, but enhance cough induced by inhaled irritants. These results are consistent with the hypothesis that activation of esophageal and nasal C-fibers contribute to cough reflex hypersensitivity observed in chronic cough patients with gastroesophageal reflux disease (GERD) and chronic rhinitis, respectively. The afferent nerves mediating cough sensitization from the esophagus are probably the neural crest-derived vagal jugular C-fibers. In addition to their responsiveness to high concentration of acid typical for gastroesophageal reflux (pH < 5), esophageal C-fibers also express receptors for activation by weakly acidic reflux such as receptors highly sensitive to acid and receptors for bile acids. The nature of sensory pathways from the nose and their activators relevant for cough sensitization are less understood. Increased cough reflex sensitivity was also reported in many patients with GERD or rhinitis who do not complain of cough indicating that additional endogenous or exogenous factors may be required to develop chronic coughing in these diseases.

Analysis of acute impact of oleoresin capsicum on rat nasal mucosa using scanning electron microscopy

Analysis of acute cellular changes seen in nasal mucosa of Wistar-Albino rats exposed to different doses of oleoresin capsicum for various time periods by means of scanning electron microscopy. Thirty-five Wistar-Albino rats were divided into five groups of seven rats each. 6-gram oleoresin capsicum per second was sprayed into cages of the groups except group 1. Spray times and duration of exposure to pepper gasses were different for each group. Thirty minutes after the exposure, the animals were killed and specimens from their nasal mucosas were harvested and examined under scanning electron microscope. Mucosal damage was scored from 0-4 points. Mean values of nasal mucosa damage scores of the groups were calculated and compared statistically. Average damage scores of the groups exposed to identical doses of oleoresin capsicum for various exposure times were compared and a statistically significant difference was seen between Groups 2 and 3 (p < 0.05), however the difference between Groups 4 and 5 was insignificant (p > 0.05). Average damage scores of the groups exposed to various doses for identical exposure times were compared, and statistically significant differences were observed between Groups 2 and 4 and also Groups 3 and 5 (p < 0.05). Outcomes of our study have demonstrated that pepper gas exerts destructive changes on rat nasal mucosa. The extent of these destructive changes increases with the prolonged exposure to higher doses. Besides, exposure time also stands out as an influential factor on the extent of the destructive changes.

The role of corneal afferent neurons in regulating tears under normal and dry eye conditions

The cornea is one of several orofacial structures requiring glandular secretion for proper lubrication. Glandular secretion is regulated through a neural reflex initiated by trigeminal primary afferent neurons innervating the corneal epithelium. Corneal sensory afferents must respond to irritating and potentially damaging stimuli, as well as drying that occurs with evaporation of the tear film, and the physiological properties of corneal afferents are consistent with these requirements. Polymodal neurons are sensitive to noxious mechanical, thermal and chemical stimuli, mechanoreceptive neurons are selectively activated by mechanical stimuli, and cool cells respond to innocuous cooling. The central terminations of corneal primary afferents are located within two regions of the spinal trigeminal nucleus. The more rostral region, located at the transition between the trigeminal subnucleus caudalis and interpolaris, represents a critical relay for the regulation of the lacrimation reflex. From this region, major control of lacrimation is carried through projections to preganglionic parasympathetic neurons located in or around the superior salivatory nucleus. Dry eye syndrome may be caused by a dysfunction in the tear secreting glands themselves or in the neuronal circuit regulating these glands. Furthermore, the dry eye condition itself may modify the properties of corneal afferents and affect their ability to regulate secretion, a possibility just now being explored.

[Allergic rhinitis. Immunological and neurogenic mechanisms]

Allergic rhinitis is one of the most common diseases to affect humans. It is important to note that it is an immunological disease which is associated with significant changes in the mucous membrane of the respiratory tract. Clinical symptoms of allergic rhinitis include sneezing, rhinorrhea, nasal itching, and nasal congestion. The mechanism underlying the development of symptoms associated with allergic rhinitis are complex, including activation and infiltration of inflammatory cells, edema, increased and altered gland activity, nerve terminal activation, triggering of neurogenic inflammation and morphologically detectable remodelling processes in the mucous membrane. Finally, a systematic activation of immune processes also takes place. Thus, allergic rhinitis is clearly a serious disease requiring prompt and effective treatment; moreover, it has been unjustly trivialized to date, not least because of its high incidence.

What are the primary clinical symptoms of rhinitis and what causes them?

The nose has a limited repertoire of responses regardless of the triggers. These responses primarily serve as a protective mechanism for the lower respiratory tract. Although the nasal reactions to pollens, particles, and pollution may have a beneficial effect for the lower airway, they create symptoms in some individuals that lead to significant morbidity. The symptoms of allergic rhinitis extend far beyond the nose, and the morbidity associated with rhinitis is significant. The nasal symptoms of rhinitis and their causes are the focus of this review.

TRPV1 and TRPA1 stimulation induces MUC5B secretion in the human nasal airway in vivo

AIM

Nasal transient receptor potential vanilloid 1 (TRPV1) stimulation with capsaicin produces serous and mucinous secretion in the human nasal airway. The primary aim of this study was to examine topical effects of various TRP ion channel agonists on symptoms and secretion of specific mucins: mucin 5 subtype AC (MUC5AC) and B (MUC5B).

METHODS

Healthy individuals were subjected to nasal challenges with TRPV1 agonists (capsaicin, olvanil and anandamide), TRP ankyrin 1 (TRPA1) agonists (cinnamaldehyde and mustard oil) and a TRP melastatin 8 (TRPM8) agonist (menthol). Symptoms were monitored, and nasal lavages were analysed for MUC5AC and MUC5B, i.e. specific mucins associated with airway diseases. In separate groups of healthy subjects, nasal biopsies and brush samples were analysed for TRPV1 and MUC5B, using immunohistochemistry and RT-qPCR. Finally, calcium responses and ciliary beat frequency were measured on isolated ciliated epithelial cells.

RESULTS

All TRP agonists induced nasal pain or smart. Capsaicin, olvanil and mustard oil also produced rhinorrhea. Lavage fluids obtained after challenge with capsaicin and mustard oil indicated increased levels of MUC5B, whereas MUC5AC was unaffected. MUC5B and TRPV1 immunoreactivities were primarily localized to submucosal glands and peptidergic nerve fibres, respectively. Although trpv1 transcripts were detected in nasal brush samples, functional responses to capsaicin could not be induced in isolated ciliated epithelial cells.

CONCLUSION

Agonists of TRPV1 and TRPA1 induced MUC5B release in the human nasal airways in vivo. These findings may be of relevance with regard to the regulation of mucin production under physiological and pathophysiological conditions.

Capsaicin-induced vasodilatation in human nasal vasculature is mediated by modulation of cyclooxygenase-2 activity and abrogated by sulprostone

Extensively based on evidence gained from experimental animal models, the transient receptor potential vanilloid receptor type 1 (TRPV1)-activator capsaicin is regarded as a valuable tool in the research on neurogenic inflammation. Although capsaicin-related drugs gained renewed interest as a therapeutic tool, there is also controversy as whether neurogenic inflammation actually takes place in humans. In this study, we verified the involvement of capsaicin in vascular responses that are regarded to be implicated in the cascade of neurogenic inflammatory mechanisms. By means of ex vivo functional experiments on human nasal mucosal vascular beds, the effect and mechanism of action of capsaicin was assessed in the absence and presence of various agents that interfere with potentially related transduction pathways. Ten micromolars of capsaicin induced vasodilatations that were reduced by the selective EP(1) prostanoid receptor antagonist SC19220 (10 μM) and almost abolished by the selective COX-2 inhibitor NS398 (1 μM) and the EP(1/3) receptor agonist sulprostone (0.1-10 nM), but not affected by the TRPV1-antagonists capsazepine (5 μM), the neurokinin NK(1) receptor antagonist GR20517A (1 μM), and the calcitonin-gene-related peptide (CGRP) receptor antagonist CGRP8-37 (100 nM). Spontaneously released PGE(2) and PGD(2) levels were significantly reduced in the presence of capsaicin. In conclusion, capsaicin-at concentrations clinically applied or under investigation for diverse disease backgrounds-induces a vasodilatory response in human nasal mucosa via a mechanism involving TRPV1-independent reduction of PGE(2) production by modulation of COX-2 enzymatic activity. These vasodilatations can be suppressed by the EP(1/3) receptor agonist sulprostone at subnanomolar concentrations.

Nasal-ocular reflexes and their role in the management of allergic rhinoconjunctivitis with intranasal steroids

Allergic rhinitis is a common disorder and involves the reaction to environmental allergens with resultant nasal and eye symptoms. The pathophysiologic mechanisms of the eye symptoms in allergic conjunctivitis include a direct effect on the eye by deposited allergen and indirect effects related to the deposition of allergen in the nasal mucosa. One of these proposed mechanisms is the existence of a nasal-ocular reflex whereby the nasal allergic reaction leads to an afferent reflex response, the efferent limb of which results in eye symptoms. Among the treatments available for allergic rhinitis, intranasal steroids are most efficacious for nasal symptoms and have also shown sizeable efficacy related to eye symptoms. We speculated that the effect of intranasal steroids on eye symptoms in allergic rhinitis was related to their inhibition of the nasal-ocular reflex and present data previously generated from our laboratory to support this assumption in a nasal challenge model.

Mometasone furoate nasal spray reduces the ocular symptoms of seasonal allergic rhinitis

BACKGROUND

Mometasone furoate nasal spray (MFNS), a potent intranasal corticosteroid with proved efficacy in relieving nasal allergic rhinitis symptoms, has demonstrated effectiveness in improving ocular symptoms associated with seasonal allergic rhinitis (SAR) in retrospective analyses.

OBJECTIVE

We sought to evaluate prospectively the efficacy of MFNS in reducing total ocular symptom scores (TOSSs) and individual ocular symptoms in subjects with SAR.

METHODS

Subjects 12 years or older (n = 429) with moderate-to-severe baseline symptoms were randomized to MFNS, 200 microg once daily, or placebo in this 15-day, double-blind, parallel-group study. Subjects evaluated morning instantaneous TOSSs and daily reflective TOSSs, total nasal symptom scores (TNSSs; both instantaneous TNSSs and reflective TNSSs, respectively), and individual ocular and nasal symptoms. Mean changes from baseline averaged over days 2 to 15 (instantaneous) and days 1 to 15 (reflective) were calculated. Quality of life was assessed by using the Rhinoconjunctivitis Quality of Life Questionnaire.

RESULTS

MFNS treatment yielded significant reductions from baseline versus placebo in instantaneous TOSSs (-0.34, P = .026, coprimary end point), instantaneous TNSSs (-0.88, P < .001, coprimary end point), reflective TOSSs (-0.44, P = .005), and reflective TNSSs (-1.06, P < .001). Significant decreases in all individual reflective ocular symptoms and instantaneous eye itching/burning and eye watering/tearing were observed for MFNS versus placebo (P < .05). Numeric improvements in instantaneous eye redness were seen but did not reach statistical significance. Improvements in Rhinoconjunctivitis Quality of Life Questionnaire total scores and individual symptom domains were achieved with MFNS treatment versus placebo (P < .001). MFNS was well tolerated.

CONCLUSION

This prospective study demonstrates that MFNS significantly reduces ocular symptoms in subjects with SAR.

Allergic conjunctivitis and the impact of allergic rhinitis

Although nasal allergy has been prominent in allergy research, ocular allergy is increasingly recognized as a distinct symptom complex that imposes its own disease burden and reduction in patients' quality of life. In the past year, knowledge of the relationships between allergic conjunctivitis and allergic rhinitis has increased. Allergic conjunctivitis is highly prevalent and has a close epidemiologic relationship with allergic rhinitis. Both conditions also exhibit similar pathophysiologic mechanisms. Pathways of communication are thought to increase the likelihood of an inflammatory reaction at both sites following allergen exposure of nasal or ocular tissue. Clinical trials of intranasal therapies have demonstrated efficacy in allergic conjunctivitis and rhinitis. Newer intranasal steroids decrease ocular symptoms, potentially achieving efficacy by suppressing the naso-ocular reflex, downregulation of inflammatory cell expression, or restoration of nasolacrimal duct patency. Proposed pathophysiologic interactions between allergic rhinitis and ocular allergy underscore the need for therapies with efficacy in both symptom sets.

Histamine in allergic rhinitis

Histamine plays a major role in allergic rhinitis. In susceptible individuals, allergen induces nasal mast cell degranulation and the release of histamine into the nasal mucosa. Histamine has been detected after controlled challenges with allergen and, when administered into the nasal cavity, elicits signs and symptoms similar to those elicited by allergen. All four histamine receptors have been demonstrated in the nasal mucosa. The role of the four histamine receptors in the pathophysiology of allergic rhinitis are discussed.

Transient receptor potential channels: targeting pain at the source

Pain results from the complex processing of neural signals at different levels of the central nervous system, with each signal potentially offering multiple opportunities for pharmacological intervention. A logical strategy for developing novel analgesics is to target the beginning of the pain pathway, and aim potential treatments directly at the nociceptors--the high-threshold primary sensory neurons that detect noxious stimuli. The largest group of receptors that function as noxious stimuli detectors in nociceptors is the transient receptor potential (TRP) channel family. This Review highlights evidence supporting particular TRP channels as targets for analgesics, indicates the likely efficacy profiles of TRP-channel-acting drugs, and discusses the development pathways needed to test candidates as analgesics in humans.

Mechanisms of the cough associated with rhinosinusitis

The diseases of the nose and paranasal sinuses (rhinosinusitis) often in combination with asthma and gastroesophageal reflux are common causes of chronic cough in patients with normal chest radiograph. The relationships between rhinosinusitis and cough are incompletely understood. We investigated modulation of the cough reflex by the inputs from the nose. We demonstrate that the cough reflex is sensitized by the intranasal administration of sensory nerve activators in animal models and in humans. Cough reflex is also sensitized in the guinea pig model of allergic nasal inflammation and in patients with allergic rhinitis. In patients with allergic rhinitis the cough sensitization is augmented during the allergen season. We conclude that the cough reflex can be sensitized from the nose. Our data indicate that this sensitization is mediated by nasal sensory nerves. We speculate that by inducing the cough reflex sensitization rhinosinusitis contributes to chronic cough. If combined with environmental or endogenous cough triggers, the cough reflex sensitization is predicted to cause excessive coughing. The potential endogenous cough triggers may be associated with rhinosinusitis (postnasal drip, aspiration of nasal secrets) or secondary to a coexistent disease such as asthma or gastroesophageal reflux.

The effects of the nasal antihistamines olopatadine and azelastine in nasal allergen provocation

BACKGROUND

Olopatadine, an antihistamine used in allergic conjunctivitis, is under development as a nasal preparation for the treatment of allergic rhinitis.

OBJECTIVES

To evaluate the efficacy of olopatadine in suppressing symptoms and biomarkers of the immediate reaction induced by nasal allergen provocation and to compare olopatadine with azelastine in the same model.

METHODS

The study was approved by the Johns Hopkins University institutional review board, and all subjects gave written consent. We studied 20 asymptomatic subjects with seasonal allergic rhinitis. The study had 2 randomized, double-blind, placebo-controlled, crossover phases that evaluated 2 concentrations of olopatadine, 0.1% and 0.2%. In a third exploratory phase, olopatadine, 0.1%, was compared with topical azelastine, 0.1%, in a patient-masked design. Efficacy variables were the allergen-induced sneezes, other clinical symptoms, and the levels of histamine, tryptase, albumin, lysozyme, and cysteinyl-leukotrienes (third study only) in nasal lavage fluids.

RESULTS

Both concentrations of olopatadine produced significant inhibition of all nasal symptoms, compared with placebo. Olopatadine, 0.1%, inhibited lysozyme levels, but olopatadine, 0.2%, inhibited histamine, albumin, and lysozyme. The effects of olopatadine, 0.1%, were comparable to those of azelastine, 0.1%.

CONCLUSIONS

Olopatadine, at 0.1% and 0.2% concentrations, was effective in suppressing allergen-induced nasal symptoms. At 0.2%, olopatadine provided evidence suggestive of inhibition of mast cell degranulation.

Nasal ocular reflexes and eye symptoms in patients with allergic rhinitis

BACKGROUND

Allergic patients often complain of eye symptoms during the allergy season. A possible mechanism for these eye symptoms is a nasal ocular reflex.

OBJECTIVE

To demonstrate eye symptoms after nasal allergen challenge.

METHODS

In a double-blind, placebo-controlled, crossover, clinical trial, 20 patients with seasonal allergic rhinitis were challenged in 1 nostril with antigen, and the response was monitored in both nostrils and in both eyes. Symptoms were recorded. Filter paper disks (intranasally) and Schirmer strips (intraocularly) were used for collecting secretions, which were subsequently eluted for the measurement of histamine and albumin levels. Patients were treated once topically at the site of challenge with azelastine or placebo.

RESULTS

After placebo treatment, ipsilateral nasal challenge caused nasal symptoms and an increase in secretion weights; both were blocked by treatment with azelastine. Histamine and albumin levels increased only at the site of nasal challenge. Azelastine pretreatment inhibited the increase in albumin but not histamine levels. Symptoms of itchy and watery eyes increased significantly compared with symptoms with sham challenge after nasal allergen and were blocked by azelastine use. Ocular secretion weights increased bilaterally after placebo use and were not inhibited by azelastine use.

CONCLUSIONS

Nasal allergen challenge releases histamine at the site of the challenge, which probably initiates a nasonasal and a nasal ocular reflex. This reflex is reduced by an H1-receptor antagonist applied at the site of the challenge. The eye symptoms associated with allergic rhinitis probably arise, in part, from a naso-ocular reflex.

Intranasal corticosteroids reduce ocular symptoms associated with allergic rhinitis

OBJECTIVE: Clinical data and recent guidelines support the positive effects of intranasal corticosteroids on allergic rhinitis-associated ocular symptoms. This article reviews the epidemiology and pathophysiology of ocular allergy symptoms and efficacy, tolerability, and potenti mechanisms of action of intranasal corticosteroids in the treatment of this condition.

DATA SOURCES: MEDLINE database.

REVIEW METHODS: A search of pertinent literature identified in vitro, preclinical, and clinical data that involve intranasal corticosteroids in ocular-related studies. Searches that used epidemiology, pathophysiology, drug class and specific agents, and other appropriate search terms were conducted.

RESULTS: Ocular symptoms, common in patients with allergic rhinitis, are associated with reduced quality of life and substantial economic costs. In the conjunctival epithelium, an early, type-1 hypersensitivity reaction occurs after direct allergen exposure. Progression to late-phase response, with recurrence of symptoms and infiltration of inflammatory cells, may occur 4 to 8 hours later and appears to be dose-related. Alteration of nasal ocular reflex pathways may also contribute to ocular symptoms in allergic rhinitis. Clinical data indicate that intranasal corticosteroids significantly reduce total and individual ocular symptoms in subjects with allergic rhinitis. Meta-analyses have found that oral/topical antihistamines are not superior to intranasal corticosteroids in reducing ocular allergy symptoms. Ocular adverse events from intranasal corticosteroids are rare.

CONCLUSION: Intranasal corticosteroids are effective and well-tolerated in the treatment of ocular symptoms associated with allergic rhinitis. Additional studies are needed to better understand the mechanisms underlying the effects of intranasal corticosteroids on ocular symptoms.

Objective monitoring of nasal patency and nasal physiology in rhinitis

Nasal obstruction can be monitored objectively by measurement of nasal airflow, as evaluated by nasal peak flow, or as airways resistance/conductance as evaluated by rhinomanometry. Peak flow can be measured during inspiration or expiration. Of these measurements, nasal inspiratory peak flow is the best validated technique for home monitoring in clinical trials. The equipment is portable, relatively inexpensive, and simple to use. One disadvantage, however, is that nasal inspiratory peak flow is influenced by lower airway as well as upper airway function. Rhinomanometry is a more sensitive technique that is specific for nasal measurements. The equipment, however, requires an operator, is more expensive, and is not portable. Thus, it is applicable only for clinic visit measures in clinical trials. Measurements require patient cooperation and coordination, and not all can achieve repeatable results. Thus, this objective measure is best suited to laboratory challenge studies involving smaller numbers of selected volunteers. A nonphysiological measure of nasal patency is acoustic rhinometry. This sonic echo technique measures internal nasal luminal volume and the minimum cross-sectional area. The derivation of these measures from the reflected sound waves requires complex mathematical transformation and makes several theoretical assumptions. Despite this, however, such measures correlate well with the nasal physiological measures, and the nasal volume measures have been shown to relate well to results obtained by imaging techniques such as computed tomography scanning or magnetic resonance imaging. Like rhinomanometry, acoustic rhinometry is not suitable for home monitoring and can be applied only to clinic visit measures or for laboratory nasal challenge monitoring. It has advantages in being easy to use, in requiring little patient cooperation, and in providing repeatable results. In addition to nasal obstruction, allergic rhinitis is recognized to be associated with impaired mucociliary clearance and altered nasal responsiveness. Measures exist for the monitoring of these aspects of nasal dysfunction. Although measures of mucociliary clearance are simple to perform, they have a poor record of reproducibility. Their incorporation into clinical trials is thus questionable, although positive outcomes from therapeutic intervention have been reported. Measures of nasal responsiveness are at present largely confined to research studies investigating disease mechanisms in allergic and nonallergic rhinitis. The techniques are insufficiently standardized to be applied to multicenter clinical trials but could be used in limited-center studies to gain insight into the regulatory effects of different therapeutic modalities.

Insights into the mechanisms of histamine-induced inflammation in the nasal mucosa

Histamine is a major autacoid released during allergic reactions. Histamine, when administered to the nasal mucosa, causes symptoms that mimic allergic rhinitis, including nasal blockage, sneezing, pruritus and rhinorrhea. This article provides an overview of the contribution of H1, H2 and H3 receptors to histamine-induced symptom generation, in particular focusing on nasal blockage.

The capsaicin cough reflex in eczema patients with respiratory symptoms elicited by perfume

Respiratory symptoms elicited by perfume are common in the population but have unclear pathophysiology. Increased capsaicin cough responsiveness has been associated with the symptoms, but it is unknown whether the site of the symptoms in the airways influences this association. The aim of this study was to investigate the association between the site of airway symptoms elicited by perfume and cough responsiveness to bronchial challenge with capsaicin. 21 eczema patients with respiratory symptoms elicited by perfume were compared with 21 healthy volunteers in a sex- and age-matched case control study. The participants completed a symptom questionnaire and underwent a bronchial challenge with capsaicin. Lower, but not upper, respiratory symptoms elicited by perfume were associated with increased capsaicin cough responsiveness. Having severe symptoms to perfume (n=11) did not relate to the site of the symptoms in the airways and was not associated with increased capsaicin cough responsiveness. In conclusion, respiratory symptoms elicited by perfume may reflect local hyperreactivity related to defensive reflexes in the airways, and measurements of the capsaicin cough reflex are relevant when patients with lower respiratory symptoms related to environmental perfume exposures are investigated.

Noxious chemical stimulation of rat facial mucosa increases intracranial blood flow through a trigemino-parasympathetic reflex--an experimental model for vascular dysfunctions in cluster headache

Cluster headache is characterized by typical autonomic dysfunctions including facial and intracranial vascular disturbances. Both the trigeminal and the cranial parasympathetic systems may be involved in mediating these dysfunctions. An experimental model was developed in the rat to measure changes in lacrimation and intracranial blood flow following noxious chemical stimulation of facial mucosa. Blood flow was monitored in arteries of the exposed cranial dura mater and the parietal cortex using laser Doppler flowmetry. Capsaicin (0.01-1 mm) applied to oral or nasal mucosa induced increases in dural and cortical blood flow and provoked lacrimation. These responses were blocked by systemic pre-administration of hexamethonium chloride (20 mg/kg). The evoked increases in dural blood flow were also abolished by topical pre-administration of atropine (1 mm) and [Lys1, Pro2,5, Arg3,4, Tyr6]-VIP (0.1 mm), a vasoactive intestinal polypeptide (VIP) antagonist, onto the exposed dura mater. We conclude that noxious stimulation of facial mucosa increases intracranial blood flow and lacrimation via a trigemino-parasympathetic reflex. The blood flow responses seem to be mediated by the release of acetylcholine and VIP within the meninges. Similar mechanisms may be involved in the pathogenesis of cluster headache.

Innervation of human nasal mucosa in environmentally triggered hyperreflectoric rhinitis

Hyperreflectoric rhinitis is related to an unspecific hyperreactivity probably caused by chemical irritants. As a major modulatory role may be attributed to the mucosal innervation, the present study was carried out to examine possible changes in the nasal mucosa innervation. Immunohistochemistry for the neuropeptides vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), substance P (SP) and neuropeptide tyrosine (NPY) revealed abundant staining of nerve fibers. Neuropeptide-contents in mucosal nerves was then quantitatively assessed and significant increases were found for SP (3.00 +/- 0.37 vs. 1.64 +/- 0.34 control group staining intensity) and VIP (2.33 +/- 0.42 vs. 0.82 +/- 0.33). In conclusion, these findings demonstrated differences in human nasal mucosa innervation between nonrhinitic and hyperreflectoric rhinitic subjects and provide evidence for a modulatory participation of neuropeptide-specific subpopulations of nerve fibers in hyperreflectoric rhinitis.

Permeability issues in nasal drug delivery

The nasal route is one of the most permeable and highly vascularized site for drug administration ensuring rapid absorption and onset of therapeutic action. It has been potentially explored as an alternative route for drugs with poor bioavailability and for the delivery of biosensitive and high molecular weight (MW) compounds such as proteins, peptides, steroids, vaccines, and so on. This review discusses the major factors affecting the permeability of drugs or biomolecules through the nasal mucosa, including biological, formulation and device-related factors. This information could potentially help to achieve desired plasma concentrations of drugs without compromising or altering the normal physiology of the nasal cavity.

Thoughts on the pathophysiology of nonallergic rhinitis

Nonallergic noninfectious rhinitis is a diagnosis by exclusion, meaning that a number of poorly defined nasal conditions that have in common allergy and infection as a cause of the rhinitis have been excluded. The etiology of some subgroups of nonallergic noninfectious rhinitis, like nonallergic rhinitis with eosinophilia (NARES) and drug-induced rhinitis, are quite well defined, but in the majority of the patients, the etiology and pathophysiology are unknown. These patients are classified as idiopathic rhinitis patients. A careful determination of the intensity of the symptoms combined with modern diagnostic tools enables us to discriminate idiopathic rhinitis patients from normal controls. This review discusses the possible pathophysicologic mechanisms of nonallergic noninfectious rhinitis, with emphasis on idiopathic rhinitis.

Riot control agents: pharmacology, toxicology, biochemistry and chemistry

The desired effect of all riot control agents is the temporary disablement of individuals by way of intense irritation of the mucous membranes and skin. Generally, riot control agents can produce acute site-specific toxicity where sensory irritation occurs. Early riot control agents, namely, chloroacetophenone (CN) and chlorodihydrophenarsazine (DM), have been replaced with 'safer' agents such as o-chlorobenzylidene malononitrile (CS) and oleoresin of capsicum (OC). Riot control agents are safe when used as intended: however, the widespread use of riot control agents raises questions and concerns regarding their health effects and safety. A large margin exists between dosages that produce harassment and dosages likely to cause adverse health effects for modern riot control agents such as CS and dibenz[b,f]1 : 4-oxazepine (CR). Yet, despite the low toxicity of modern riot control agents, these compounds are not entirely without risk. The risk of toxicity increases with higher exposure levels and prolonged exposure durations. Ocular, pulmonary and dermal injury may occur on exposure to high levels of these substances, and exposure to riot control agents in enclosed spaces may produce significant toxic effects. Reported deaths are few involving riot control agents, and then only under conditions of prolonged exposure and high concentrations. Recently, concern has focused on the deaths resulting from law enforcement use of OC, a riot control agent generally regarded as safe because it is a natural product. As with other xenobiotics, not enough is known concerning the long-term/chronic effects of riot control agents. Clearly, there is considerable need for additional research to define and delineate the biological and toxicological actions of riot control agents and to illuminate the full health consequences of these compounds as riot control agents.

Intranasal capsaicin is lacking therapeutic effect in perennial allergic rhinitis to house dust mite. A placebo-controlled study

In a recent placebo-controlled study we demonstrated that capsaicin is an efficacious substance in the treatment of non-allergic non-infectious rhinitis. In this study the therapeutic effect lasted more than 9 months. This effect was not based on modulation of inflammation. To evaluate the effect of repeated application of capsaicin to patients with a nasal allergy to house dust mites (HDM), using the same treatment protocol as recently introduced in the treatment of non-allergic patients. Twenty-six patients with rhinitis, 15 females and 11 males (range: 20-46 years; mean 30.5), allergic to HDM were treated with either capsaicin or placebo in a double-blind, placebo-controlled, parallel group design. Nasal reactivity to HDM expressed as nasal symptoms, albumin and leukotriene levels in nasal lavage fluid and responsiveness to histamine, assessed as symptoms before and 6 weeks after treatment, were used to compare both treatment groups. In addition, visual analogue scales and rhinitis quality of life (RQL) assessment before, 6 weeks after and 3 months after treatment were used as outcome variables. No significant effect of capsaicin on nasal challenge tests with HDM (nasal symptoms, albumin and leukotriene levels), on VAS or RQL outcome 6 weeks or 3 month's after treatment, was demonstrated. Capsaicin did have a small effect on the area of the curve (AUC) of histamine dose response curves (P = 0.03). Desensitization with capsaicin in doses sufficient to control symptoms in patients with severe non-allergic rhinitis is lacking therapeutic effect in perennial allergic rhinitis.

Comparison of the response to histamine challenge of the nose and the maxillary sinus: effect of loratadine

To study the response of the maxillary sinus to histamine provocation, we performed a double-blind, randomized, crossover trial during which nonallergic subjects without symptoms of rhinitis (n = 25) received either 10 mg loratadine or placebo once daily for a week and then underwent nasal challenge with histamine (3, 10, and 30 mg/ml) followed, 24 h later, by a maxillary sinus challenge while still receiving the medication. Nasal challenge with histamine led to significant increases in vascular permeability, reflex nasal secretions, sneezing, and other nasal symptoms. Sinus challenge resulted in significant increases in vascular permeability within the sinus cavity (P < 0.01) and some nasal symptoms but no significant change in reflex nasal secretions. The response of the sinus mucosa to histamine was lower in magnitude than that of the nose. Treatment with loratadine resulted in a significant inhibition of the histamine-induced changes in both nasal and sinus cavities. Our data suggest the lack of a sinonasal reflex response to histamine provocation of the maxillary sinus of nonallergic individuals.

Toxicologic evaluation of pepper spray as a possible weapon for the Dutch police force: risk assessment and efficacy

The efficacy and possible health risks of pepper spray were evaluated. In a number of countries, pepper spray is being used by police forces to aid in arresting aggressive individuals. Pepper spray is commercially available as a canister filled with Capsicum extract, which contains capsaicin as the active component. When applied in the form of a spray, it causes an acute inflammation, and humans involuntarily close their eyes, experience a burning feeling on the skin, and are usually rapidly incapacitated. Use by the U.S. police was successful in subduing aggressive individuals in 90% of cases, and a reduction of injury to both police and arrested individuals was noted. In general, pepper spray appeared to be a relatively safe weapon with small risk of causing acute physical harm. Despite this evidence, a number of fatalities were reported in the United States following the use of pepper spray. However, it was concluded that it was not the pepper spray but rather other factors such as drugs and hog-tying that contributed to the cause of death. In only 1 case, that of an asthmatic man, was it concluded that the use of pepper spray contributed to the cause of death. Much attention has been paid to possible genotoxic effects of Capsicum extract such as mutagenicity and carcinogenicity. It was concluded that the risk of long-term health effects is negligible. Because pepper spray may induce bronchoconstriction, people suffering from chronic obstructive lung disease may be hypersensitive to it. Although the results of one study indicate that asthmatics do not develop additional bronchoconstriction following inhalation of capsaicin, the number of experimental data are too few to draw sound conclusions.

Effect of route of breathing on response to exposure in a swine confinement building

Exposure of naive subjects to swine buildings results in acute nasal, lung, and peripheral blood inflammatory responses with an increase in nonallergic airway responsiveness. Because nasal passages filter large particles and soluble gases and because swine building exposure results in an acute inflammatory response at this level, we questioned what effect breathing through or avoiding this route would have on local and systemic inflammation. Nine normal young men 23 to 37 yr of age were exposed for 5 h to a swine building, once breathing normally and once with the mouth occluded (n = 8) (Protocol 1) or the nose occluded (n = 4) (Protocol 2); three subjects participated in both protocols. For each protocol each subject underwent a methacholine challenge for PC20 measurement, a nasal lavage, venous blood puncture, and a bronchoalveolor lavage (BAL) once before and once after each swine building exposure. Bronchial responsiveness as measured by PC20 decreased in most subjects after swine building exposure and was not influenced by the route of breathing. Nasal lavage neutrophils increased tenfold after each swine exposure, except when the nose was occluded where no alteration was observed. Total BAL cells significantly increased after each exposure to the swine building, this increase was not modified by the route of breathing. In Protocol 1, white blood cells increased from a baseline level of 7.0 to 10.5 x 10(9) cells/L after exposure with normal breathing and to 10.7 x 10(9) cells/L during nasal breathing exclusively. For Protocol 2, these respective values were: 5.6, 11.7 and 10.4 x 10(9)/L. Interleukins 6 and 8 levels in BAL, nasal washes, and serum were increased by swine building exposure, except in the nasal wash when the nose was occluded. In conclusion, the lung and blood responses to exposure in a swine confinement building are not modified by the route of breathing, suggesting that nasal inflammation and filtration are not important in the process and that small respirable particles and/or gases may be responsible for these responses.

Plasma extravasation through neuronal stimulation in human nasal mucosa in the setting of allergic rhinitis

We have previously shown that capsaicin nasal challenge in subjects with allergic rhinitis produces a dose-dependent increase in the albumin content of nasal lavage fluids. In the present set of studies, we determined whether this observation represents plasma extravasation that is neuronally mediated. To evaluate whether glandular secretions contribute to the albumin increase in nasal lavage fluids, volunteers with allergic rhinitis were pretreated with atropine or placebo before capsaicin challenge. Atropine significantly reduced the volume of returned lavage fluids and their lysozyme content but increased their albumin and fibrinogen content. To assess the contribution of sensory nerve stimulation, subjects with allergic rhinitis were pretreated in a second study with lidocaine or placebo before capsaicin challenge. Lidocaine significantly attenuated the capsaicin-induced increases in the volume of nasal lavage fluids, as well as their lysozyme and albumin content. To rule out the possibility of a direct effect of lidocaine on blood vessels rather than on nerves, healthy subjects were pretreated in a third study with lidocaine or placebo before bradykinin nasal challenge. Lidocaine did not affect the bradykinin-induced increase in the albumin content of nasal fluids. We conclude that, in allergic rhinitis, high-dose capsaicin induces plasma extravasation in the human nose and that this effect is neuronally mediated. This provides more definitive evidence that neurogenic inflammation can occur in vivo in the human upper airway.

Comparison of nasal mucosal responsiveness to neuronal stimulation in non-allergic and allergic rhinitis: effects of capsaicin nasal challenge

BACKGROUND

Neuronal involvement has been implicated in the pathophysiology of non-allergic and allergic rhinitis, contributing to the typical exacerbation of these conditions upon exposure to non-specific environmental irritants.

OBJECTIVES

To determine if non-allergic and allergic rhinitis are characterized by increased responsiveness of the nasal mucosa to sensorineural stimulation.

METHODS

Nasal challenges with capsaicin and its vehicle were performed in three groups of subjects -- non-allergic rhinitics, perennial allergic rhinitics, and healthy controls -- and resultant symptom scores, glandular secretion reflected by lactoferrin levels, and plasma extravasation reflected by albumin levels in nasal lavage fluid were compared.

RESULTS

Capsaicin-sensitive nerve stimulation produced increases in symptom scores and lactoferrin levels which were similar among the three groups of subjects. On the other hand, only the group of subjects with allergic rhinitis demonstrated a significant capsaicin-induced increase in albumin levels and a trend in total protein levels.

CONCLUSIONS

We conclude that non-allergic rhinitis is not characterized by increased responsiveness of capsaicin-sensitive nerve fibres; while allergic rhinitis is marked by hyperresponsiveness manifested as increased albumin leakage in nasal fluids. This may reflect the activity of an axonal reflex to sensorineural stimulation.

Dose-dependent effects of capsaicin nasal challenge: in vivo evidence of human airway neurogenic inflammation

BACKGROUND

Nerve involvement has been implicated in the pathophysiology of chronic respiratory inflammatory diseases. Peptidergic nerve stimulation has been shown to induce leukocyte activation and plasma extravasation in the airways of various animal species. The occurrence of this phenomenon of neurogenic inflammation in the human airway, however, has not been established.

OBJECTIVE

We conducted this study to determine whether neuronal stimulation can induce reproducible and dose-dependent inflammatory changes in the human upper airway.

METHODS

Ten volunteers with active allergic rhinitis participated in the study. Capsaicin, the pungent component of hot pepper that specifically stimulates afferent nerve fibers, was administered by means of nasal spray in doses of 1 microg, 10 microg, and 100 microg in a double-blind, randomized, crossover manner with 1 week between doses. Symptom scores before and after capsaicin nasal challenge were recorded by using visual analog scales. Nasal lavage fluids collected before and at 30 minutes, 1 hour, and 4 hours after capsaicin challenge were analyzed for leukocyte counts; albumin and lysozyme levels were measured to evaluate effects on plasma leakage and gland secretion, respectively.

RESULTS

Capsaicin nasal challenge produced symptoms of burning, congestion, and rhinorrhea. Leukocyte counts or albumin and lysozyme levels were not significantly increased after administration of 1 microg of capsaicin at any time point. On the other hand, there were significant increases in leukocyte counts 1 hour (p < 0.05) and 4 hours (p = 0.008) after 10 microg of capsaicin and 30 minutes (p = 0.009), 1 hour (p = 0.007), and 4 hours (p = 0.007) after 100 microg of capsaicin. Albumin and lysozyme levels were both significantly increased 30 minutes after 10 microg and 100 microg of capsaicin (p = 0.005 for both). Comparison of changes in symptom scores, leukocyte counts, and albumin and lysozyme levels among the three capsaicin challenges indicated generally increasing effects with higher capsaicin doses.

CONCLUSION

Capsaicin-sensitive nerve stimulation in subjects with active allergic rhinitis produces reproducible and dose-dependent leukocyte influx, albumin leakage, and glandular secretion. These results provide in vivo evidence for the occurrence of neurogenic inflammation in the human upper airway with active allergic disease.

Nonallergic rhinitis. Pathophysiology and models for study

Nonallergic rhinitis is a diagnosis of exclusion which is given to patients who suffer perennial nasal congestion, rhinorrhea, and/or sneezing with no identifiable allergic etiology. Because there is still no clear understanding of the pathophysiology, it is possible that a number of different disease processes may be included within this clinically defined entity. This report does not attempt to present an overall discussion of the clinical approaches to patients with nonallergic rhinitis. Instead, an outline is presented of various research approaches which may be used in its study. A number of nasal provocation models using nonallergic stimuli are available for application in the laboratory. These include intranasal methacholine challenges, intranasal histamine challenges, nasal inhalation of cold dry air, and intranasal capsaicin challenges. These models provide certain insights into mechanisms of nonallergic hyper-responsiveness. An additional approach to the study of nonallergic rhinitis is to examine available therapies, allowing the clinician to evaluate various pathways of importance in the disease process. These approaches provide a certain understanding of this common but perplexing entity, although further study is still required.