Hemorrhagic stroke caused by xylometazoline poisoning

An increase in the use of over-the-counter medications has been observed in recent years. This also concerns xylometazoline, approved for the treatment of allergic rhinitis or upper respiratory tract infections. We present the fatal case of a 40 year-old-woman with a massive hemorrhagic stroke. Initial toxicology tests of biological material collected during autopsy revealed the presence of xylometazoline. No other significant toxicology findings were noted. LC-MS/MS method has been developed to determine xylometazoline concentration, which was 18.6 ng/mL in blood and 498.9 ng/mL in urine. The macroscopically detected hemorrhagic focus was confirmed by histopathological which confirmed hemorrhagic infarcts in the brain tissue, especially in the subarachnoid area. No other pathological changes were found. Based on findings from autopsy and toxicological analyses, the direct cause of death was concluded to be hemorrhagic stroke resulting from xylometazoline intoxication. Although xylometazoline products are regarded as relatively safe and are available over the counter, the risk of adverse effects, in particular stroke leading to death, should be considered. If adverse effects are observed, it is reasonable to measure the concentration of the drug in blood and urine. With such data, it will be possible to assess the actual exposure to this xenobiotic and draw firmer conclusions.

International consensus statement on allergy and rhinology: Allergic rhinitis - 2023

BACKGROUND

In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document.

METHODS

ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work.

RESULTS

ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost.

CONCLUSION

The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment.

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.

Does oxymetazoline increase the efficacy of nasal steroids in treating nasal polyposis?

BACKGROUND

Although nasal steroids are the mainstay treatments in nasal polyposis, up to one-half of patients do not respond and need surgical treatment. This study aimed to evaluate whether oxymetazoline administration produces any additive effect on nasal steroid therapy and whether rebound congestion develops after oxymetazoline treatment.

METHODS

Sixty-eight patients with nasal polyposis were randomly assigned in a 1:1 ratio to receive either oxymetazoline plus mometasone furoate nasal spray (MFNS) or placebo plus MFNS, 2 sprays per nostril twice daily, with an interval of 5 minutes between each medication for 4 weeks. All the patients were then treated with MFNS, 2 sprays per nostril twice daily for 2 weeks. The nasal symptoms score, peak inspiratory flow index, nasal mucociliary clearance time (NMCCT), and total nasal polyps score were used to evaluate treatment outcomes. An intention-to-treat analysis was performed, and a worst case sensitivity analysis was applied to missing cases.

RESULTS

Thirty-four patients were allocated to the oxymetazoline-MFNS group, and 34 to the placebo-MFNS group. One patient in each group was lost to last-visit follow-up. At 4 weeks after beginning treatment, the oxymetazoline-MFNS group showed significantly greater improvement in blocked nose, hyposmia, peak flow, NMCCT, and total nasal polyps score than the placebo-MFNS group. During the nasal steroid phase, both groups showed continuing improvement in all outcome variables. However, the oxymetazoline-MFNS group still showed significantly greater improvement in blocked nose, hyposmia, NMCCT, and total nasal polyps score, but not peak flow, than the placebo-MFNS group at the end of the study.

CONCLUSION

The use of nasal steroids with oxymetazoline was more effective over 6 weeks than nasal steroids alone in improving blocked nose, hyposmia, nasal mucociliary clearance, and polyp size in treatment of nasal polyposis. There was no evidence of rebound congestion after 4 weeks of oxymetazoline treatment.

Determination of oxidative stress and effect of erdosteine on rhinitis medicamentosa in a rat model

We aimed to determine the presence of oxidative stress in rhinitis medicamentosa (RM) and to evaluate the effect of erdosteine (ED) on mucosal changes in a rat model. Twenty-four male rats were used in this experimental study. Three groups were created. Group 1 (n=8) was the control group. Two puffs of 0.05% oxymetazolin were sprayed into the nasal cavities of the remaining rats (n=16) three times daily for eight weeks. One of these 16 rats was scarified at the end of the eight weeks and examined to confirm the presence of RM. Seven of the remaining 16 rats were killed, and venous blood samples were taken (Group 2). Group 3 (n=8) received 10mg/kg of an ED suspension orally for seven days. All rats were put on formalin for light microscopy. The total antioxidant status (TAS) was similar in all groups (p=0.073). The total oxidative status (TOS) of the RM group was significantly higher than that of the control group and RM+ED group (Group 3) (p=0.003 and p=0.011, respectively). The pathological recovery of the nasal mucosa of the rats was similar in the RM+ED and control groups. The TOS was high in this RM rat model, and oxidative stress was associated with RM. ED significantly ameliorated nasal mucosal changes induced by RM, suggesting that oxidative stress may play an important role in the pathophysiology of this condition.

Topical glucocorticoid reduces the topical decongestant-induced histologic changes in an animal model nasal mucosa

OBJECTIVES/HYPOTHESIS

To investigate the histologic consequences of simultaneous nasal glucocorticosteroid and xylometazoline HCl administration in the rabbit nasal mucosa.

STUDY DESIGN

Prospective randomized study.

METHODS

Twenty New Zealand male rabbits were randomly placed into three groups: group I, control (n = 6); group II, xylometazoline HCl (n = 8); or group III, xylometazoline HCl-fluticasone furoate (n = 6). Group I received no treatment. Groups II and III received two intranasal puffs of xylometazoline HCl 0.5 mg/mL twice daily or two puffs of xylometazoline HCl 0.5 mg/mL twice daily plus one puff of 27.5 μg fluticasone furoate twice daily to each nostril (110 μg), respectively. At the end of 3 weeks, the rabbits were sacrificed. The mucosa of the nasal cavities was excised. Specimen sections (5 μm) were stained with hematoxylin and eosin, mucicarmine, and Gomori one-step trichrome and were examined under a light microscope. The presence of edema, congestion, inflammatory cell infiltration, nasociliary loss, epithelial and nerve-ending degeneration, and goblet cell increase were evaluated semiquantitatively (grades 0-3).

RESULTS

Statistically significant differences were detected between groups II and III in terms of edema, congestion, inflammatory cell infiltration, nasociliary loss, and epithelial degeneration (P = .006, P = .049, P = .015, P = .014, and P = .049, respectively). Nerve-ending degeneration, goblet cell increase, and quantitative goblet and neutrophil cell counts did not yield statistically significant differences between groups II and III (P = .137, P = .580, P = .770, and P = .616, respectively).

CONCLUSIONS

The combined simultaneous intranasal administration of xylometazoline HCl and fluticasone furoate appears to be beneficial in minimizing the long-term usage-associated congestion, edema, inflammatory cell infiltration, epithelial degeneration, and nasociliary loss in the rabbit model nasal mucosa.

New aspects of the Slug Mucosal Irritation assay: predicting nasal stinging, itching and burning sensations

Stinging, itching and/or burning (SIB) sensations cannot be detected by animal tests or in vitro models. In the past, the Slug Mucosal Irritation (SMI) assay demonstrated a relation between an increased mucus production in slugs and an elevated incidence of SIB sensations in humans. A new 1-day SMI test procedure was developed focusing on the prediction of these short-term sensations. The objective of this study was to verify whether this new procedure is capable predicting mucosal tolerance of several marketed nasal formulations using the slug Arion lusitanicus. Irritation and tissue damage were quantified with a 5-day repeated exposure study by means of the mucus produced and proteins and enzymes released. The new protocol predicted SIB sensations by means of mucus production. The effects of six liquid nasal formulations were tested with both protocols, while five physiologic saline solutions were only tested with the new protocol to optimize it. None of the tested liquid nasal formulations resulted in tissue damage; however, exposure to the different formulations had a clear effect on the mucus production of the slugs and moderate discomfort was observed in some cases. These effects were due to the active ingredient, the presence of benzalkonium chloride as a preservative or the hyperosmolality of the formulation. For the most part results agreed with clinical data found in literature. It was concluded that the SMI assay, and the new 1-day protocol in particular, is a good tool to predict nasal clinical discomfort.

Influence of intranasal sterile isotonic sea water applications on xylometazoline administration: an experimental study in pigs

OBJECTIVE

The aim of this study was to investigate how isotonic sea water solution (Physiomer) affects the structure of porcine nasal mucosa when it is applied simultaneously with vasoconstrictors (xylometazoline) for a prolonged period of time.

METHODS

Twenty pigs of the PMR-Landraze breed formed the study group. A solution of xylometazoline 0, 1% (Otrivin spray, Novartis) was sprayed every 8h in both nasal cavities of the pigs, with two applications into each nostril for 28 days. Between the applications (4h later), the right nasal cavity was washed with sterile isotonic sea water (Physiomer Normal, Geomar). Biopsies were taken under endoscopic guidance from the nasal mucosa of each nasal cavity separately at specific times. Five histological parameters were microscopically examined for each biopsy section: (1) inflammation, (2) fibrosis, (3) metaplasia of the epithelium, (4) reactive atypia of the epithelium and (5) necrosis.

RESULTS

Statistically significant differences regarding grade of inflammation on days 7 (p=0.0009), 12 (p=0.01), 20 (p=0.02) and 28 (p=0.0005), regarding grade of fibrosis on day 28 (p=0.026) and regarding epithelial metaplasia on day 5 (p=0.052) were found between the nasal mucosa treated only with vasoconstrictors and the nasal mucosa treated with vasoconstrictors and sea water washing. In all cases, samples from the nasal cavities that had been washed with Physiomer appeared with a lower grade of inflammation, fibrosis and metaplasia compared to the samples from nasal mucosa where no nasal washing was performed.

CONCLUSION

Nasal irrigations with isotonic sea water, when are applied 4h after vasoconstrictors for a long period of time, prevent nasal mucosa from histological damage.

Rhinitis medicamentosa: therapeutic effect of diode laser inferior turbinate reduction on nasal obstruction and decongestant abuse

BACKGROUND

The purpose of this study was to evaluate long-term outcomes of an outpatient-based diode laser inferior turbinate reduction (ITR) in therapy-refractory rhinitis medicamentosa (RM).

METHODS

In a prospective clinical investigation, 42 consecutive RM patients underwent videoendoscopic ITR with a diode laser after topical anesthetic preparation. Intra- and perioperative details were recorded including the occurrence of bleeding, crusting, pain, or discomfort. Treatment efficiency was assessed by follow-ups 1 and 6 weeks as well as 6 and 12 months after surgery. Subjective pre- and posttherapeutic nasal airflow (NA) and patient satisfaction were rated on visual analog scales (VASs). Assessment of the long-term objective clinical effectiveness was based on rhinomanometry, IT photodocumentation, and the recurrent need for decongestants.

RESULTS

Preoperative addiction to decongestants lasted 5 +/- 2 years (mean +/- SD). There was no major bleeding requiring nasal packing, and there were no other perioperative complications. Postoperative edema disappeared within the 1st week and crusting within 6 weeks after surgery. VAS was characterized by very low values for intraoperative pain and discomfort and high postoperative patient satisfaction. After 6 months, NA data revealed a significant improvement of subjective VAS and objective rhinomanometry (250.4-413.9 cm3/s inspiration at 150 Pa). A total of 88% of patients managed to successfully stop decongestant abuse after 6 months (74% after 1 year).

CONCLUSION

In therapy-refractory RM, outpatient diode laser ITR of hyperplastic IT represents a highly effective, safe, and well-tolerated treatment option that provides long-lasting recovery by markedly improving NA and stopping addiction to nasal decongestants.

Rhinitis medicamentosa: a review of causes and treatment

Rhinitis medicamentosa (RM) is a drug-induced, nonallergic form of rhinitis that is associated with prolonged use of topical vasoconstrictors, i.e. local decongestants. Symptoms are exacerbated by the preservative benzalkonium chloride (BKC) in the nasal preparations. Nasal stuffiness is caused by rebound swelling of the mucosa when the decongestive effect of the drug has disappeared. To alleviate this symptom, patients gradually start using larger doses of the vasoconstrictor more frequently. In many cases, the patient is unaware of the condition, thus entering a vicious circle of self-treatment. Careful questioning is required during consultation to establish diagnosis. The pathophysiology of the condition is unclear; however, vasodilatation and intravascular edema have both been implicated. Management of RM requires withdrawal of topical decongestants to allow the damaged nasal mucosa to recover, followed by treatment of the underlying nasal disease. Topical corticosteroids such as budesonide and fluticasone propionate should be used to alleviate rebound swelling of the nasal mucosa. Where possible, avoiding exposure to BKC is recommended.

A study of the effect of nasal steroid sprays in perennial allergic rhinitis patients with rhinitis medicamentosa

OBJECTIVE

To determine if rebound congestion can be reduced with concomitant nasal steroid spray usage.

STUDY DESIGN AND SETTING

Randomized, double blind, controlled single center study.

PARTICIPANTS

Twenty subjects with perennial allergic rhinitis with nasal congestion.

INTERVENTION

All subjects received 3 weeks of twice-daily oxymetazoline. After 2 weeks, subjects were randomized to 2 additional weeks of concomitant budesonide aqueous nasal spray (n = 9) or placebo (n = 10). In the sixth week, all sprays were stopped.

RESULTS

Both groups showed subjective and objective evidence of rebound congestion 24 hours after cessation of oxymetazoline (P < 0.05). Subjective rebound congestion resolved in 48 hours in the budesonide aqueous nasal spray group but persisted for over 1 week in the placebo group.

CONCLUSION

Rebound congestion is objectively present in patients with perennial allergic rhinitis after 3 weeks of oxymetazoline spray. Rebound congestion is reduced by concomitant budesonide aqueous nasal spray use.

SIGNIFICANCE

This study supports the common clinical practice of nasal steroid sprays to ameliorate rebound congestion concomitant with and after cessation of topical decongestant sprays.

Rhinitis medicamentosa: aspects of pathophysiology and treatment

With modern vasoconstrictors, such as oxy- and xylometazoline, the risk of developing rhinitis medicamentosa (RM) has been considered to be small or even nonexistent. However, recent studies have shown that overuse of these drugs may result in rebound congestion, nasal hyperreactivity, tolerance, and histologic changes of the nasal mucosa. Using rhinostereometry, it has also been shown that the long-term use of the preservative benzalkonium chloride (BKC) in oxymetazoline nasal spray accentuates the severity of rhinitis medicamentosa in healthy volunteers. A nasal decongestant spray composed of a combination of vasoactive substances and BKC has a long-term adverse effect on the nasal mucosa. BKC alone induces mucosal swelling after 30 days use of the nasal spray in healthy subjects, unlike placebo. According to the author, rhinitis medicamentosa can be defined as a condition of nasal hyperreactivity, mucosal swelling, and tolerance that is induced, or aggravated, by the overuse of topical vasoconstrictors with or without a preservative. An adequate treatment of these patients consists of a combination of vasoconstrictor withdrawal and a topical corticosteroid to alleviate the withdrawal process. The underlying nasal disorder must then be treated. Patients with rhinitis medicamentosa who overuse topical decongestants and are able to stop using such drugs should be careful about taking these drugs again, even for a few days. They must be informed about the rapid onset of rebound congestion upon repeated use in order to avoid the return of the vicious circle of nose-drop abuse.

One year follow-up of patients with rhinitis medicamentosa after vasoconstrictor withdrawal

The aim of the study was to systematically follow-up 10 patients with rhinitis medicamentosa for at least 1 year after vasoconstrictor withdrawal. During withdrawal of the decongestants the patients used budesonide nasal spray, 400 micrograms/day, for 6 weeks. The thickness of the nasal mucosa, the decongestive effect of oxymetazoline, and the histamine sensitivity were measured with rhinostereometry during the period. The thickness of the nasal mucosa and the symptom scores of nasal stuffiness were reduced considerably 6 and 12 months after vasoconstrictor withdrawal. The histamine sensitivity reflecting nasal hyperreactivity was still increased after 6 months, but not after 1 year. The decongestive effect of oxymetazoline increased after 6 months, indicating reversible tolerance. We conclude that when given adequate treatment and information about nose-drop overuse, all patients were able to stop using the vasoconstrictors and no one relapsed into a daily long-term overuse of vasoconstrictors during the 1-year follow-up period.

Effect on the nasal mucosa of long-term treatment with oxymetazoline, benzalkonium chloride, and placebo nasal sprays

A parallel, randomized, double-blind study was performed in 30 healthy subjects to investigate the effects on the nasal mucosa of a 1-month treatment with nasal sprays. Ten subjects received oxymetazoline nasal spray; 10 subjects used a nasal spray containing the preservative benzalkonium chloride, and the others were treated with a placebo nasal spray. The three variables that were studied --nasal mucosal swelling, symptom scores, and nasal reactivity-- were estimated by histamine challenge before and after 28 days of treatment. Rhinostereometry was used to measure nasal mucosal swelling and nasal reactivity. After 28 days of use, benzalkonium chloride spray alone induced an increase in nasal mucosal swelling. At the end of the month, the score for nasal stuffiness was significantly higher for the group treated with oxymetazoline than for those treated with benzalkonium chloride. Oxymetazoline nasal spray induced a pronounced increase in nasal reactivity, which was significantly greater than that induced in the placebo group. Long-term use of placebo and benzalkonium chloride nasal sprays also caused an increase in nasal reactivity, but not to the same extent as with the nasal sprays containing oxymetazoline. The authors concluded that long-term use of oxymetazoline induces a sensation of nasal stuffiness, which may be due to unconscious exaggeration of the degree of nasal stuffiness, induced nasal hyperreactivity, or a combination of both. These factors are probably the main reasons for the prolonged use of nasal decongestive sprays and the development of rhinitis medicamentosa. Benzalkonium chloride induces mucosal swelling, which explains why the presence of this preservative in a decongestant spray aggravates rhinitis medicamentosa.

Effect of oxymetazoline nose drops on acute sinusitis in the rabbit

This investigation was designed to evaluate the effect of the common topical nasal decongestant oxymetazoline hydrochloride on the early local tissue defense in an experimental bacterial infection. For that purpose, a bilateral infection of the maxillary sinus was induced in 14 rabbits. Nose drops (oxymetazoline) were instilled in one nasal cavity, and placebo in the other. After 48 hours, the degree of infection was judged by using a semiquantitative inflammatory score to evaluate histologic preparations of the maxillary sinuses. On the oxymetazoline-treated side, we found a significantly higher degree of inflammation. We conclude that oxymetazoline nose drops, commonly used in acute rhinitis and sinusitis, interfere with the normal defense mechanisms during bacterially induced sinusitis, possibly by a decrease in mucosal blood flow.

The pathophysiology and treatment of rhinitis medicamentosa

To evaluate the treatment of rhinitis medicamentosa, 10 consecutive patients discontinued their use of topical vasoconstrictors and were treated with budesonide nasal spray, 400 micrograms, daily for 6 weeks. The thickness of the nasal mucosa, the decongestive effect of oxymetazoline and the histamine sensitivity were measured with rhinostereometry. All patients were able to stop using the vasoconstrictors and objective variables showed that they needed treatment for at least 6 weeks. The results strongly support the theory that the rebound swelling is due to interstitial oedema rather than to vasodilatation. The presence of tachyphylaxis reflected by a reduction in both the decongestive effect of oxymetazoline and a reduction of drug duration was seen.

Benzalkonium chloride in a decongestant nasal spray aggravates rhinitis medicamentosa in healthy volunteers

A randomized double-blind parallel study with 20 healthy volunteers was performed to research the effect of a preservative in a decongestant nasal spray on the development of rhinitis medicamentosa. Ten subjects received oxymetazoline nasal spray with benzalkonium chloride and the others used oxymetazoline nasal spray without the preservative three times daily for 30 days. Before starting the course of treatment and after its conclusion, recordings of the mucosal surface positions were made with rhinostereometry followed by histamine challenge tests. Symptoms of nasal stuffiness were estimated on visual analogue scales (0-100) in the morning and the evening just before using the nasal spray. After 30 days, rebound swelling and nasal stuffiness were found in both groups. In the group receiving oxymetazoline nasal spray with benzalkonium chloride the mean rebound swelling was 1.1 mm and the estimated mean evening symptom score for nasal stuffiness was 43. In the group without benzalkonium chloride the corresponding variables were significantly less marked, with a mean rebound swelling of 0.5 mm (P < 0.05) and a mean evening symptom score of 25 (P < 0.05). The increase in histamine sensitivity in both groups was interpreted as a sign of nasal hyperreactivity. A new type of nasal spray bottle was used that has been shown to prevent bacterial contamination. In conclusion, the long-term use of benzalkonium chloride in oxymetazoline nasal spray accentuates the severity of rhinitis medicamentosa in healthy volunteers.

Benzalkonium chloride in nasal decongestive sprays has a long-lasting adverse effect on the nasal mucosa of healthy volunteers

Twenty healthy volunteers participated in the present study on the long-term effects of a nasal decongestive spray composed of either a combination of oxymetazoline nasal spray and benzalkonium chloride or of oxymetazoline nasal spray alone. Three months before the present study the participants had undergone treatment with nasal decongestants for 4 weeks. Ten of the subjects had been treated with oxymetazoline nasal spray without benzalkonium chloride and 10 of them had been treated with oxymetazoline nasal spray with benzalkonium chloride. In a double-blind study the subjects who had been treated with oxymetazoline nasal spray and benzalkonium chloride were again treated with the same combination of substances as before, and the subjects who had been treated with oxymetazoline nasal spray alone were also treated again with oxymetazoline nasal spray alone, but on this occasion only for 10 days. Three variables were studied before and after the 10 days of treatment, i.e. nasal mucosa congestion, nasal reactivity and symptom scores. It was found that only the subjects who were treated with the combination of oxymetazoline nasal spray and benzalkonium chloride had increased nasal stuffiness, estimated by symptom scores and measurements of nasal mucosa swelling after 10 days of treatment. It is concluded that a nasal decongestant spray composed of a combination of vasoactive substance and benzalkonium chloride has a long-term adverse effect on the nasal mucosa.

Four-week use of oxymetazoline nasal spray (Nezeril) once daily at night induces rebound swelling and nasal hyperreactivity

A randomized double-blind parallel study with 20 healthy volunteers was performed to examine the effect of oxymetazoline nasal spray on the development of rhinitis medicamentosa. For 30 days, 10 subjects were given oxymetazoline nasal spray once daily at night and placebo in the morning and at noon, while the others used oxymetazoline nasal spray three times daily. Before and after the course of treatment, the mucosal surface positions were determined with rhinostereometry, followed by histamine challenge tests. In the morning and the evening just before use of the nasal spray, symptoms of nasal stuffiness were evaluated on visual analogue scales (0-100). After 30 days, rebound swelling and nasal stuffiness were found in both groups. In the group receiving oxymetazoline nasal spray once daily at night, the mean rebound swelling was 0.8 mm (p < 0.01) and the estimated mean symptom score for nasal stuffiness in the evening was 43 (p < 0.05). In the group receiving the same nasal spray three times daily, the mean rebound swelling was 1.1 mm (p < 0.01) and the mean evening symptom score was 43 (p < 0.05). The finding of an increase in histamine sensitivity in both groups was taken to indicate nasal hyperreactivity. There was no significant difference in the investigated variables between the two groups. It is concluded that the risk of developing rebound swelling and nasal hyperreactivity remains, whether oxymetazoline nasal spray is used once or three times a day for 30 days.