Contact allergy to neomycin sulfate: results of a multifactorial analysis

Contact allergy to neomycin in consecutively patch tested Danish eczema patients from 2000 to 2023: A cross-sectional study

BACKGROUND

Neomycin is an aminoglycoside antibiotic that may cause contact allergy. It was withdrawn as a medicine for human use in Denmark in October 2009 but is still found in some vaccines.

OBJECTIVES

To identify time trends in contact allergy to neomycin in the period from 2000 to 2023.

METHODS

A cross-section study of patients ≥18 years consecutively patch-tested with neomycin sulfate (20% in pet.) at Gentofte Hospital, Denmark, during the period 2000-2023 was conducted.

RESULTS

The overall prevalence of contact allergy to neomycin was 1.4%. The prevalence was significantly lower in the period '2010-2023' (1.2%) than in '2000-2009' (1.8%) (p < 0.005). Contact allergy to neomycin was significantly positively associated with facial dermatitis and age >40 years, and significantly negatively associated with occupational dermatitis and hand dermatitis. No changes in sex, occupational dermatitis, atopic dermatitis, hand dermatitis, leg dermatitis, facial dermatitis, or age > 40/≤40 (the MOAHLFA-index) were identified when comparing neomycin contact allergic-patients in the two periods '2010-2023' and '2001-2009'.

CONCLUSION

Neomycin is a rare cause of contact allergy in Denmark with a significantly lower prevalence following its withdrawal as a medicinal product for human use in Denmark in 2009.

Clinico-Epidemiological Profile of Allergic Contact Dermatitis and Its Correlation With Patch Testing in a Tertiary Care Center in Eastern India

BACKGROUND

Allergic contact dermatitis (ACD) is one of the most common skin disorders seen among patients attending dermatology clinics in India. Patch testing is the gold standard for diagnosing ACD. The clinical-epidemiological pattern of ACD and the allergen-causing it may be different in different geographic locations. Finding the profile of allergens commonly causing ACD in a particular region will help to formulate prevention strategies for the development of ACD.

AIM AND OBJECTIVE

The primary aim of the study was to find out the clinical-epidemiological distribution of allergic contact dermatitis and to identify the common allergens causing it by patch testing in this region of India.

MATERIALS AND METHODS

A total of 111 cases of ACD were included in the study. Clinico epidemiological profiles of all patients were documented. The patch testing was performed in the outpatient department using the antigens of the Indian Standard Series kit (Systopic Laboratories Pvt. Ltd., New Delhi, India). Patches were removed after 48 hours (two days) of application. The first reading was taken 15 to 20 minutes after the removal of patches on day two. A second reading was taken on day four (96 hours of application) to confirm the presence of an allergic reaction.  Results: The patch test was found to be positive in 69% of cases. It was observed that male persons from lower socioeconomic status were getting ACD on most accounts. Potassium dichromate (PDC) was found to be the most common allergen (30.43%) followed by parthenium (26.08%), para-phenylenediamine (PPD) (21.73%), nickel sulfate (18.84%), chlorocresol (15.94%), black rubber (14.49%), cobalt sulfate (13.04%), and wool alcohols (7.24%) respectively.

CONCLUSION

Our study showed potassium dichromate is the commonest allergen causing ACD in this part of the country. The importance of patch testing lies mainly in educating the patient regarding the avoidance of exposure to particular allergens to avoid the development of new ACD as well as an exaggeration of pre-existing ACD.

Efficacy of plasma activated saline in a co-culture infection control model

Plasma activated liquids have demonstrated antimicrobial effects and receive increasing attention due to the potential to strengthen the armoury of novel approaches against antibiotic resistant bacteria. However, the antibacterial activity and cytotoxic effects of these solutions need to be understood and balanced before exposure to humans. In this study, the antibacterial effects of plasma activated saline (PAS) were tested against Gram negative and positive bacteria, and HaCaT keratinocytes were used for cytotoxicity studies. For the first time, a co-culture model between these bacteria and eukaryotic cells under the influence of PAS has been described. Exposure of saline to plasma resulted in high concentrations of nitrate, hydrogen peroxide and a reduction of pH. PAS caused high antibacterial effects in the co-culture model, accompanied by high cytotoxic effects to the monolayer of mammalian cells. We present evidence and provide a deeper understanding for the hypothesis that upon treatment with PAS, chemical species generated in the liquid mediate high antimicrobial effects in the co-culture setup as well as mitochondrial depolarization and glutathione depletion in HaCaT cells and cell lysis due to acidic pH. In conclusion, PAS retains strong antibacterial effects in a co-culture model, which may have unintended negative biological effects on mammalian cells.

Immediate and Delayed Hypersensitivity Reactions to Antibiotics: Aminoglycosides, Clindamycin, Linezolid, and Metronidazole

Hypersensitivity reactions including IgE-mediated and delayed cell-mediated reactions to aminoglycosides, clindamycin, linezolid, and metronidazole are rare. For aminoglycosides, allergic contact dermatitis is the most frequent reaction for which patch testing can be a useful step in evaluation. For clindamycin, delayed maculopapular exanthems are the most common reactions. There are case reports of clindamycin associated with drug rash with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP), acute febrile neutrophilic dermatosis, and symmetrical drug-related intertriginous and flexural exanthema (SDRIFE). For linezolid, cases of hypersensitivity were exceedingly rare and included urticaria, angioedema, anaphylaxis, delayed rashes, and DRESS. For metronidazole, only rare cases were found across a broad spectrum of reactions including allergic contact dermatitis, fixed drug eruption, angioedema, anaphylaxis, serum sickness-like reaction, SJS/TEN, AGEP, SDRIFE, and a possible case of DRESS. IgE-mediated reactions and anaphylaxis to these types of antibiotics are uncommon, and reports of skin testing concentrations and desensitization protocols are largely limited to case reports and series. Non-irritating skin testing concentrations have been reported for gentamycin, tobramycin, and clindamycin. Published desensitization protocols for intravenous and inhaled tobramycin, oral clindamycin, intravenous linezolid, and oral and intravenous metronidazole have also been reported and are reviewed.

Topical Antibacterials in Dermatology

Topical antibacterials are commonly used for superficial pyodermas such as impetigo and treatment or prevention of infections following minor cuts, abrasions, burns, and surgical wounds. Several antibiotics and antiseptics are available for use in different indications. One of the major uses of topical antibacterials is acne in which benzoyl peroxide is the drug of the first choice either singly or in combination with antibiotics or retinoids. Mupirocin and fusidic acid are the two most commonly used antibiotics for the treatment of superficial pyodermas and eradication of staphylococcal carrier state. Bacterial resistance to topical antibiotics is a growing concern and topical antiseptics such as gentian violet are getting renewed interest as alternatives. Incidence of contact dermatitis is a limiting factor for the use of several topical antibacterials. Although many botanical products have demonstrated in vitro activities against skin pathogens, their clinical utilities remain to be established by good-quality clinical trials.

Patch test results with the European baseline series and additions thereof in the ESSCA network, 2015-2018

BACKGROUND

Clinical surveillance of the prevalence of contact allergy in consecutively patch tested patients is a proven instrument to continually assess the importance of contact allergens (haptens) assembled in a baseline series.

OBJECTIVES

To present current results from the European Surveillance System on Contact Allergies, including 13 countries represented by 1 to 11 departments.

METHODS

Anonymized or pseudonymized patch test and clinical data from various data capture systems used locally or nationally as transferred to the Erlangen data centre were pooled and descriptively analysed after quality control.

RESULTS

In the 4 years (2015-2018), data from 51 914 patients patch tested with the European baseline series (EBS) of contact allergens were analysed. Contact allergy to nickel was most frequent (17.6% positive), followed by contact allergy to fragrance mix I (6.9%), methylisothiazolinone (MI; 6.2%), and Myroxylon pereirae resin (balsam of Peru; 5.8%).

CONCLUSIONS

While the prevalence of MI contact allergy decreased substantially following regulatory intervention, the persistently high levels of allergy to metals, fragrances, other preservatives, and rubber chemicals point to problems needing further research and, potentially, preventive efforts. Results with national additions to the baseline series provide important information on substances possibly to be considered for inclusion in the EBS.

Contact Dermatitis after Prescription of an Ophthalmic Ointment Containing Fradiomycin Sulfate: A Retrospective Database Study Using Japanese Health Insurance Claims Data

BACKGROUND

Topical ointments containing fradiomycin sulfate, such as fradiomycin sulfate/methylprednisolone (F/M) and fradiomycin sulfate/betamethasone sodium phosphate (F/B), are known to cause allergic contact dermatitis (CD) in some patients, especially when used for the periocular region. F/M is commonly prescribed to patients for various conditions; however, there are no reports with respect to the incidence of CD caused by F/M in actual practice.

OBJECTIVE

The aim was to investigate the incidence of CD using a data-based retrospective cohort study.

METHODS

Using a Japanese health insurance claims database [MinaCare Co. Ltd. healthcare database (MinaCare HDB)], a comparative assessment was conducted of F/M and another combination drug (F/B) and two single-drug treatments (ophthalmic ointments with either an antibiotic or a steroid). The total data set consisted of 1,176,082 individuals in the MinaCare HDB, with 54,016 having received prescriptions for one of the four investigational drug regimens.

RESULTS

Overall, the incidences of CD were similar in three of the four groups in this study (F/M 0.091; F/B 0.092; steroids 0.102), while being lower in the fourth group (antibiotics 0.060). Even after confirmation of a diagnosis of CD, prescriptions for the investigational drugs were repeatedly filled for some patients.

CONCLUSION

This study demonstrated that there was no clear difference in the incidence of CD after filling prescriptions for F/M, F/B, and ophthalmic ointment containing a steroid, while the incidence with antibiotics was lower by 0.03-0.04 compared with the other groups. Considering the observation that the investigational drugs were repeatedly prescribed even after the diagnosis of CD, it is critical that the risk of CD with these prescribed topical ointments is better understood by primary care physicians in order to take appropriate countermeasures.

Neomycin, polymyxin B, and dexamethasone allergic reactions following periocular surgery

Background

The aim of this study was to evaluate the rate of periocular allergic skin reactions to topical neomycin, polymyxin B, and dexamethasone (NPD) ophthalmic ointment.

Methods

A consecutive patient prospective study was performed. A total of 522 patients who had a procedure involving incision of the periocular skin with subsequent postoperative application of NPD ophthalmic ointment were included. Patients were evaluated for signs of allergy at 1 week postoperatively or prior if the patient had complaints. A periocular allergic reaction was defined as any periocular skin pruritus, erythema, edematous papules, vesicles, or plaques at the site of ointment application beyond that of the typical postprocedure presentation. The patients continued to be monitored for 30 days postoperatively.

Results

Of the 522 patients who completed the study, eight (1.5%) had a definitive periocular allergic contact dermatitis to the NPD ophthalmic ointment. Allergic presentation ranged from postoperative day 3 to 14.

Conclusions

The rate of periocular allergic reactions to NPD ophthalmic ointment is significantly lower than reported in the literature for other topical preparations of neomycin and polymyxin B. The low rate of allergy in this study suggests that NPD ophthalmic ointment can safely be applied to the periocular skin with a very minimal risk of inciting an allergic reaction.

Surgery-Related Contact Dermatitis: A Review of Potential Irritants and Allergens

Surgical procedures utilize an increasing number of medical products including antiseptics, anesthetics, gloves, suture materials, tissue adhesives, topical antibiotics, and bandages. Many of these products have irritant potential. Allergic contact dermatitis has also been reported. This review covers preoperative, operative, and postoperative exposures that may result in contact dermatitis. Testing with standard patch panels such as T.R.U.E. Test and the North American Contact Dermatitis Group 65 allergen series does not evaluate for all relevant contactants. A thorough understanding of potential exposures is vital to effectively evaluate a patient with surgery-related contact dermatitis. A systematic approach is needed to ensure that standard patch panels and supplementary patches adequately address each encountered contactant.

Decreasing Rates of Neomycin Sensitization in Western Canada

Background:

Neomycin contact sensitization rates in North America range from 7% to 13%, whereas in Europe they average approximately 1.9%.

Objectives:

Given that topical neomycin products are no longer readily available in Canada, the aim of this study was to examine what influence this may have had on neomycin sensitization rates in the 3 western provinces.

Methods:

On the basis of an observation originally communicated by L. M. Parsons and C. Zhang of the University of Calgary, which suggested significantly reduced rates of neomycin sensitization in Calgary, Alberta, Canada, a multicenter study of patch test results from 5690 patient charts was undertaken. Data from 3 other western Canadian Universities (the University of Saskatchewan, the University of Alberta, and the University of British Colombia) were analyzed. Data were available from 2001 to 2013 for the University of Saskatchewan (except 2006), whereas the University of Alberta and the University of British Columbia had data from 2009 to 2013. Descriptive statistics, trend analysis, and risk estimates were determined using SPSS version 20.

Results:

Sensitization rates for neomycin have decreased in western Canada and are now similar to those of Europe.

Conclusions:

This trend is likely influenced by the reduced availability of over-the-counter and prescription neomycin products in Canada.

Topical triple-antibiotic ointment as a novel therapeutic choice in wound management and infection prevention: a practical perspective

Triple-antibiotic ointment (TAO) is a safe and effective topical agent for preventing infections in minor skin trauma. The formulation contains neomycin, polymyxin B and bacitracin in a petrolatum base. TAO is active against the most common disease-causing pathogens found in wounds and on the skin and may be an attractive alternative to oral therapy in select circumstances. Resistance to TAO does not develop readily, and safety studies have shown that the risk of allergic sensitivity to TAO is low. Susceptibility profiles of TAO have remained relatively unchanged since its discovery. Prophylaxis or treatment with TAO should be considered as resistant organisms continue to emerge in the community and hospital setting.

Hypersensitivity reactions to non beta-lactam antimicrobial agents, a statement of the WAO special committee on drug allergy

Antibiotics are used extensively in the treatment of various infections. Consequently, they can be considered among the most important agents involved in adverse reactions to drugs, including both allergic and non-allergic drug hypersensitivity [J Allergy Clin Immunol 113:832–836, 2004]. Most studies published to date deal mainly with reactions to the beta-lactam group, and information on hypersensitivity to each of the other antimicrobial agents is scarce. The present document has been produced by the Special Committee on Drug Allergy of the World Allergy Organization to present the most relevant information on the incidence, clinical manifestations, diagnosis, possible mechanisms, and management of hypersensitivity reactions to non beta-lactam antimicrobials for use by practitioners worldwide.

Immunomodulatory effects of antimicrobial agents. Part I: antibacterial and antiviral agents

Despite impressive therapeutic progresses in the battle against infections, microorganisms are still a threat to mankind. With hundreds of antibacterial molecules, major concerns remain about the emergence of resistant and multidrug-resistant pathogens. On the other hand, the antiviral drug armamentarium is comprised of only a few dozens of compounds which are highly pathogen specific, and resistance is also a concern. According to Arturo Casadevall (Albert Einstein College of Medicine, NY, USA), we have now entered the third era of anti-infective strategy, which intends to favor the interplay between active molecules and the immune system. The first part of this review focuses on the potential immunomodulating properties of anti-infective agents, beginning with antibacterial and antiviral agents.

Allergic contact dermatitis: epidemiology, molecular mechanisms, in vitro methods and regulatory aspects. Current knowledge assembled at an international workshop at BfR, Germany

Contact allergies are complex diseases, and one of the important challenges for public health and immunology. The German ‘Federal Institute for Risk Assessment’ hosted an ‘International Workshop on Contact Dermatitis’. The scope of the workshop was to discuss new discoveries and developments in the field of contact dermatitis. This included the epidemiology and molecular biology of contact allergy, as well as the development of new in vitro methods. Furthermore, it considered regulatory aspects aiming to reduce exposure to contact sensitisers. An estimated 15–20% of the general population suffers from contact allergy. Workplace exposure, age, sex, use of consumer products and genetic predispositions were identified as the most important risk factors. Research highlights included: advances in understanding of immune responses to contact sensitisers, the importance of autoxidation or enzyme-mediated oxidation for the activation of chemicals, the mechanisms through which hapten-protein conjugates are formed and the development of novel in vitro strategies for the identification of skin-sensitising chemicals. Dendritic cell cultures and structure-activity relationships are being developed to identify potential contact allergens. However, the local lymph node assay (LLNA) presently remains the validated method of choice for hazard identification and characterisation. At the workshop the use of the LLNA for regulatory purposes and for quantitative risk assessment was also discussed.

Allergic contact dermatitis in children: common allergens and treatment: a review

PURPOSE OF REVIEW

The following study reviews the recent literature pertaining to allergic contact dermatitis (ACD) in the pediatric population. This study also provides an overview of the most common allergens and discusses various therapeutic modalities.

RECENT FINDINGS

The pathophysiology of ACD is intricate and multifaceted, resulting in a characteristic, delayed inflammatory response. Although commonly recognized in adults, its existence in the pediatric population was questioned. Recent literature suggests that pediatric ACD exists and is more common than previously recognized. The diagnosis relies on the clinical presentation combined with appropriate use and interpretation of a patch test. Although many studies have investigated ACD in children, few have documented the relevance of positive patch test reactions until recently. The most current prevalence estimates of positive patch test reactions range from 14 to 70% of children patch tested. Although that range is broad, these studies have demonstrated the relevance of positive reactions and confirmed ACD as a disease entity in children.

SUMMARY

ACD is a previously underrecognized disease process in the pediatric population that can manifest as a serious dermatologic challenge for both patients and physicians. This review will address the prevalence, diagnostic methods, frequent allergens and treatment options in pediatric ACD.

Prevalence of patch test results from 1970 to 2002 in a multi-centre population in North America (NACDG)

BACKGROUND

The North American Contact Dermatitis Group (NACDG) has members who assess subjects with suspected allergic contact dermatitis (ACD) and patch tests them with the same screening allergens using a standardized procedure permitting analysis of long-term trends in patch test reactions.

OBJECTIVE

This study reports the trends in prevalence patch test positivity of allergens by pooling data collected by the NACDG between 1970 and 2002.

PATIENTS/METHODS

Patients were tested with the screening series of allergens, using a standardized technique. Data from these patients were recorded on a standard computer entry form and analysed. More than 100 allergens were tested on over 34,000 patients during several patch studies between the period. The Cochran-Armitage test of trend is used to evaluate changes in prevalence over time.

RESULTS

4 trends are noticed: (1) The incidence of presumed allergic nickel (P < 0.0001) and quaternium-15 (P < 0.0001) reactions rose with consistency over the years. (2) While that of cinnamic aldehyde (P = 0.21) and p-phenylenediamine (P < 0.0001) decreased. (3) The prevalence of positive reactions for potassium dichromate (P < 0.0001) shows an initial steady decrease but then a sharp increase starting from the 1996 period. (4) In contrast, thiuram (P = 0.0008) and neomycin (P < 0.0001) show an initial general increase, with a sharp decrease between 1998 and 2002.

CONCLUSION

Implications for opportunities to prevent ACD by utilizing less-allergenic alternatives appear robust; however, we do not wish to over generalize interpretations because of important limitations.

Polysensitization and increased susceptibility in contact allergy: a review

Genetic factors presumably play a role in contact allergy (CA). There is, however, a lack of conclusive evidence from clinical studies. This may be on account of the strongly competing or modifying impact of exogenous factors, namely the potency of allergens and the intensity of exposure, and the fact that - in principle - everybody can be sensitized. Regarding phenotype, in contrast, polysensitization (PS) seems to indicate a subset of individuals at greater risk. In human sensitization experiments with dinitrochlorobenzene, induction was facilitated in PS, and elicitation enhanced. Recent clinical epidemiological data, taking confounders for PS, such as age, sex, and other skin diseases into account, demonstrated the following: (i) PS was the greatest risk factor to be sensitized to a number of (even weak) index allergens, indicating higher susceptibility on the level of induction; (ii) patch test reactions in PS patients were generally stronger indicating higher susceptibility on the level of elicitation. These findings are complemented by reports on polymorphisms of TNF-alpha and IL-16 in PS patients. Future studies on the genetics of CA should be performed in subgroups with PS, focussing on polymorphisms relevant for CA-specific and nonspecific (inflammatory) processes.

The epidemiology of contact allergy in the general population--prevalence and main findings

A substantial number of studies have investigated the prevalence of contact allergy in the general population and in unselected subgroups of the general population. The aim of this review was to determine a median prevalence and summarize the main findings from studies on contact allergy in the general population. Published research mainly originates from North America and Western Europe. The median prevalence of contact allergy to at least 1 allergen was 21.2% (range 12.5-40.6%), and the weighted average prevalence was 19.5%, based on data collected on all age groups and all countries between 1966 and 2007. The most prevalent contact allergens were nickel, thimerosal, and fragrance mix. The median nickel allergy prevalence was 8.6% (range 0.7-27.8%) and demonstrates that nickel was an important cause of contact allergy in the general population and that it was widespread in both men and women. Numerous studies demonstrated that pierced ears were a significant risk factor for nickel allergy. Nickel was a risk factor for hand eczema in women. Finally, heavy smoking was associated with contact allergy, mostly in women. Population-based epidemiological studies are considered a prerequisite in the surveillance of national and international contact allergy epidemics.

Allergic contact dermatitis to topical antibiotics: Epidemiology, responsible allergens, and management

Topical antibiotics are widely used to treat cutaneous, ocular, and otic infections. Allergic contact dermatitis to topical antibiotics is a rare but well-documented side effect, especially in at-risk populations. The purpose of this article is to review the epidemiology, responsible allergens, and management of allergic contact dermatitis to topical antibiotics.

LEARNING OBJECTIVE

After completing this learning activity, participants should be able to describe the epidemiology of allergic contact dermatitis related to topical antibiotics; show knowledge of the most common allergenic topical antibiotics; and understand the allergenic cross-reactivity pattern amongst topical antibiotics.

A further characteristic of susceptibility to contact allergy: sensitization to a weak contact allergen is associated with polysensitization. Results of the IVDK

Although genetic factors probably account for differences in susceptibility to contact allergy, they have not yet been identified, partly due to an insufficient understanding of 'susceptibility'. Regarding polysensitization (PS) as a sign of increased susceptibility, we studied the relationship between PS and sensitization to weak versus strong allergens. Patch test data from 66,835 patients registered by the multicentre project, Information Network of Departments of Dermatology (IVDK) between 1 January 1997 and 31 December 2004, were analysed. The association between the number of sensitization to standard series allergens, and contact allergy to a strong allergen methyldibromoglutaronitrile (MDBGN) and to a weak allergen (paraben mix), was analysed with adjusted logistic regression analysis. In paraben-positive (++/+++) patients, the risk of > or = 2, > or = 3 or > or = 4 additional reactions were significantly increased by a factor of 2.1-4.6 compared to MDBGN-sensitized (++/+++) patients. Varying the basic model, a higher risk of additional positive reactions associated with paraben sensitization was consistently identified. The association between PS and sensitization to weak allergens adds a further characteristic of susceptibility to former findings of the IVDK, where PS was related to an increased risk of induction, elicitation, and cytokine polymorphisms. PS can be regarded as a phenotype to be considered in genetic studies.

Contact allergy to topical drugs: prevalence in a clinical setting and estimation of frequency at the population level

OBJECTIVES

To estimate the prevalence of contact allergy (CA) to a set of topical drugs patch tested in the research network IVDK (Information Network of Departments of Dermatology; www.ivdk.org) between 1995 and 2004, and to extrapolate these clinical data to the German population.

METHODS

Clinical data comprised results of allergy patch tests with topical drugs in patients with suspected CA. Clinical epidemiology and drug utilization research (CE-DUR) methods were employed to grossly estimate the incidence of CA to these topical drugs during two 5-year periods (1995-1999 and 2000-2005) in the German general population. To estimate the number of persons eligible for patch testing (with the topical drugs) on a general population level, sales data of patch test material were obtained. By relating this denominator to the CA frequency observed in the IVDK, the incidence of CA to selected topical drugs in the German general population was crudely estimated.

RESULTS

In general, topical aminoglycosides showed the highest CA frequencies and, except for gentamicin sulfate, frequencies of CA to all other allergens tested were lower in the 2nd period of analysis. According to the medium model, 1-year incidence rates ranged from 1 (hydrocortisone-17-butyrate) to 29 persons/100,000 (neomycin sulfate) in the general population (1995-1999).

CONCLUSION

The CE-DUR approach yielded incidence estimates of CA to relevant topical drugs in the German general population, which, despite their limited precision in absolute terms, illustrate the relative frequency of this particular adverse effect. However, comparative risk assessment should preferably take exposure information into account.

Relationship of patch test positivity in a general versus an eczema population

Using previously generated data from multicenter studies European Environmental and Contact Dermatitis Research Group (EECDRG) and North American Contact Dermatitis Group (NACDG), we compare patch test positivity of random sample and eczema populations, attempting to ascertain how one might extrapolate frequency from an eczema group to a general population. We included population-based mathematical estimates for patch test reaction in the general population using the Multinational MONItoring of trends and determinants in Cardiovascular disease MONICA and Clinical Epidemiology and Drug-Utilization Research (CE-DUR) systems. Data analysis provides a ratio of eczema population:random sample population for each allergen and an overall ratio of all allergens 5:1 for actual data and 6:1 for population-based estimates (according to the MONICA and CE-DUR systems). If the positivity rate were the same in each population, the ratio would approximate 1. The individual allergen ratios ranged from formaldehyde at 11.6 to parabens at 1.0, with respect to the NACDG. Some differences may be explained by exposure (neomycin) being greater in patients than in random population. Materials of ubiquitous exposure - i.e. fragrance mix and nickel - had ratios closer to 1. Taken together, data obtained in eczema patients may be viewed as part of a complex biology and may eventually be of use in aiding validation of predictive dermatotoxilogic assays and in public health assessments.

A high-positive patch test load correlates with further positive patch test reactions irrespective of their location

BACKGROUND

Patch testing is the standard clinical procedure to prove contact sensitization. It is a common practice to attach multiple patch tests at the same time. However, synchronous reactions to unrelated allergens may not be completely unassociated. If so, the reaction in a given test field might be influenced by other positive test reactions in a distance-related degree. This article analyses whether there is a distance-related effect of synchronous positive patch test reactions on the outcome of a target patch test.

METHODS

Data collected from patients patch tested for diagnostic purposes with 15 standard allergens attached in a specific pattern between 1992 and 2004 in 20 centres in a Central European network were retrospectively evaluated. The association between the target patch test result (allergic vs negative reaction to the thiuram mix) and the number and cumulated strength of synchronous positive reactions (positive patch test load) to allergens placed in nearby or distant positions to the target patch was analysed by using logistic regression analysis.

RESULTS

The likelihood of a positive reaction to thiuram mix significantly increased with an increasing synchronous positive patch test load generated by positive reactions to allergens unrelated to thiuram mix. The effect of allergens neighbouring the target allergen was not significantly stronger than that of allergens placed in distant positions.

CONCLUSION

For the interpretation of patch test results, the potentially enhancing effects of a synchronous positive patch test load should be considered. The local distribution of the patches on the back is, however, not critical.