Bruce Brod’s research while affiliated with University of Pennsylvania and other places

Allergic contact dermatitis represents a T cell-mediated, delayed-type hypersensitivity response to exogenous agents. While allergic contact dermatitis is one of the most common causes of skin disease encountered by dermatologists, emerging trends within the field are in constant flux, as influenced by ever-changing industry practices and evolving consumer behaviors. Although certain allergens continue to predominate, new chemicals are frequently being introduced, thus shifting the pattern of allergen exposure and sensitization. This review examines the impact of trends in new and emerging contact allergens, with particular attention to clinical contexts in which these agents may be encountered. In addition, we offer a working knowledge of these allergens' characteristics, sources, and relevance, while outlining recommendations to accurately evaluate, diagnose, and provide appropriate counseling for these diseases.

Background: Differences in patterns of allergic contact dermatitis (ACD) among underrepresented minority populations are not well studied. Objective: The aim of the study was to investigate patterns of ACD in African American and White patch-tested patients in a distinct metropolitan area over a 10-year period. Methods: We conducted a retrospective review of 297 ACD patients patch tested from 2009 to 2019. Differences in allergen frequency, relevance, and sources of exposure were evaluated. Fisher exact test analyses were performed to examine these differences. Results: Among 297 patients, 215 were White and 47 were African American. The most common sensitizers differed between the 2 groups. African American patients also reacted with statistically significant greater frequency to disperse dye blue (P = 0.019) and textile dye mix (P = 0.001). The most common source of positive patch tests for all patients was personal care products (72%). Occupational allergy was greater in African American male patients, and personal care product exposure was greater in White male patients (P = 0.009). Conclusions: Our study highlights the differing patterns of sensitization seen in African American and White patients. This is likely due to differences in personal care product use or occupational allergy. Additional studies with larger sample sizes are needed to expand upon these differences.

Patch testing is the gold standard diagnostic tool for cell-mediated type IV hypersensitivity reactions like ACD. These individuals have primed antigen-specific T lymphocytes that cause a reaction when antigens are applied to the skin due to prior sensitization. Patch testing can be used in both the adult and pediatric population, but it is contraindicated in patients with a known history of severe allergic reactions to suspected allergens, generalized active dermatitis, or extensive eczema. Patch test systems can be a comprehensive (70-80 allergens) panel but can also be targeted and limited to a more common allergen series (35 allergens). The decision for allergen selection should be based on careful patient history, physical exam, and availability of allergens. Measurement and interpretation of the test results requires training and experience, as well as consideration of relevance and clinical history. Patch testing is considered generally safe with just a few known complications: excited skin syndrome, active sensitization, rarely anaphylaxis and other cutaneous complications. Appropriate pretesting patient education can help to mitigate some of these complications. Based on patch testing results, patients should be educated regarding proper allergen avoidance measures to resolve symptoms of ACD.

Allergic contact dermatitis is the fifth most common skin condition of patients seeking medical treatment in the United States. Patch testing is usually performed by dermatologists using one of three baseline series including the Thin-layer Rapid Use Epicutaneous (TRUE) test, the North American Contact Dermatitis Group (NACDG) series, or the American Contact Dermatitis Society (ACDS) baseline series with the latter two series employing 70 or 80 allergens, respectively. Both the NACDG and ACDS series have mostly the same allergens with few differences in composition and concentration and capable of detecting 80% of all relevant contact allergies in the United States. Both of these series are modified every 2 years based on published prevalence data. Compared to the International Contact Dermatitis Research Group (ICDRG) or the European Baseline Series (EBS), both of the baseline series used in the United States are broader and larger though most expert-level patch testers across the globe expand well beyond the baseline series depending on the patient exposure and/or occupation to increase the sensitivity of patch testing.

The American Contact Dermatitis Society Core Allergen series was introduced in 2013 and updated in 2017. Changes in our recommended allergens are again necessary, taking into account data from the American Contact Dermatitis Society's Contact Allergen Management Program top 100 allergens from 2018. For the updated series, we removed methyldibromoglutaronitrile and added new haptens: Lyral, Limonene, Linalool, carmine, benzyl salicylate, disperse yellow 3, jasmine, peppermint, pramoxine, shellac, and lauryl polyglucose (glucosides). These additional allergens should increase the yield of relevant positive reactions for our patients.

We thank Drs Gore and Cohn for their interest in our article¹ and thoughtful comments. We agree that ongoing research is needed; however, we would like to point out several issues. First, many parabens are, in fact, not banned in the European Union. The European Union has banned 5 longer-chain parabens not because of evidence that they are unsafe, but rather because “no information was submitted by industry for the safety evaluation [of these compounds].”² All of the most commonly used parabens, including methylparaben, ethylparaben, propylparaben, and butylparaben, along with many others, are considered safe and legal for use as preservatives in Europe.² Although many researchers in the clean beauty movement have expressed concerns about the potential for endocrine disruption by parabens, studies in rats and yeast cells have shown parabens to be thousands to millions of times weaker than estradiol, an endogenous sex hormone.³ Given that women are exposed to much more potent natural estrogens, along with estrogens in oral contraceptive pills and even phytoestrogens in food, the extremely weak estrogenicity of parabens is unlikely to be meaningful. The Cosmetic Ingredient Review has done an extensive investigation of the scientific literature on paraben safety and has concluded that parabens are safe in personal care products. The US Food and Drug Administration has also concluded that parabens are safe when used in personal care products.

Background: The American Contact Dermatitis Society Contact Allergen Management Program (CAMP) database was developed to provide patients with safe alternative products free of selected contact allergens. However, the CAMP database also records valuable information including the frequency of contact allergen searches for patients. Objectives: The aim of the study was to determine the relative prevalence of contact allergens in North America. Methods: Data from the CAMP database were analyzed from January 1, 2018, to January 1, 2019. The number of searches performed for each specific allergen served as a measure of the relative prevalence for each contact allergen. Results were then stratified by age, sex, atopic history, and patch screening tray used. Results: The 2018 CAMP data show that many of the prevalent allergens are not currently on any contact allergy screening series. These data strongly indicate that testing only to an 80-item screening series will not provide adequate care for many patients with contact allergy. The most prevalent contact allergens seen were fragrance mix, nickel, balsam of Peru, methylchloroisothiazolinone/methylisothiazolinone, and cobalt. Some important differences are seen when stratifying CAMP data by age, sex, atopic history, and patch screening tray used. Limitations: Possible sources of data error exist because of lack of uniformity of patch test practices. Conclusions: The CAMP database can be used to determine the relative prevalence of contact allergens, to help develop North American core screening patch test series, and to document the medical necessity of more comprehensive patch testing for patients with recalcitrant contact allergy. Capsule summary:

Background: Patch testing is the criterion standard for diagnosis and management of allergic contact dermatitis. Limitations on the number of allergens tested can negatively impact patient care. Objective: This study reports clinical practice patterns of American Contact Dermatitis Society (ACDS) members. Methods: In October and November 2018, the US-based members of the ACDS received an electronic survey regarding their procedures and experiences with patch testing. We evaluated the type of practice, number of patients tested, type of screening and supplemental series, number of allergens tested, and billing and reimbursement concerns. Results: There were 149 respondents; 62% use ACDS Core 80, 70% "sometimes" or "always" test with supplemental series, and 70% "sometimes" or "always" test patient products. Participants estimated that supplemental series identify relevant allergens 35% of the time. Approximately 66% most commonly test more than 81 allergens per patient, and 78% expressed concerns regarding fair reimbursement. Conclusions: Most ACDS members routinely test more than 81 allergens per patient. Barriers to fair payment for beyond a fixed number of patches at any one visit may impede the diagnosis of allergic contact dermatitis, prolong suffering, and worsen outcomes.