Children With AD More Likely to React to at Least 1 Allergen During Patch Testing, Study Says

Children with atopic dermatitis (AD) developed more positive patch test (PPT) reactions, and are more likely to react to at least 1 allergen during patch testing, compared with children without AD, according to a study published in the Journal of the American Academy of Dermatology.

The researchers explained that AD and allergic contact dermatitis (ACD) are common inflammatory diseases diagnosed in children. Although ACD is prevalent in 16.5% of the general child population, less than 10% receive patch testing. They partially correlated this to the difficulty in clinically distinguishing between AD and ACD as both cause children to develop red, itchy, eczema-like patches and plaques on the skin. Consequently, physicians may not perform patch testing as a child’s ACD case may be misconstrued to be AD, resulting in ACD being underdiagnosed.

Also, historically, physicians believed that AD and ACD could not co-occur due to being mediated by opposing TH1 and TH2 immunologic divisions. Although physicians now understand that the pathophysiology of both diagnoses is far more complex and intricate, the prevalence of ACD in children with AD vus those without AD is still largely unknown. Because of this, the researchers conducted a retrospective case-control study to “evaluate the prevalence of ACD in children with AD compared to those without AD and to determine if there are particular allergens more commonly positive in children with AD.”

Child with atopic dermatitis

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The study population consisted of 912 children referred for patch testing between January 1, 2018, and December 31, 2022, from 14 geographically diverse centers in the United States. Of the population, 615 (67.4%) children had AD and 297 (32.6%) did not. The researchers noted that both the AD and non-AD groups had a similar gender distribution, with 62% girls and 38% boys overall.

Experienced physicians or advanced practice providers who performed the patch tests applied the allergens either to the patient’s back or the proximal extremities depending on whether the AD limited the surface area on their back. Researchers defined PPT as “the presence of erythema, infiltration, papules, and vesicles or bullae” and calculated the PPT rate by taking the sum of patients positive for the respective allergens and dividing it by the number of patients tested for that specific allergen.

Through this study, the researchers found that children with AD who received patch testing were more likely to have more than 1 positive reaction (odds ratio [OR], 1.57; 95% CI, 1.14-2.14; P = .005) and a greater number of positive results overall (2.3 vs 1.9; P = .012) than those without AD. Their findings demonstrated several differences in the prevalence of certain allergens within children with and without AD. Notably, children with AD were more likely to be patch test–positive for bacitracin (OR, 3.23; 95% CI, 1.12-9.35; P = .030), carba mix (OR, 3.36; 95% CI, 1.17-9.70; P = .025), and cocamidopropyl betaine (OR, 3.69; 95% CI, 1.74-7.84; P = .0007).

Additionally, the researchers determined that children with AD were more likely to have atopic comorbidities than those without it: asthma (OR, 3.09; 95% CI, 2.02-4.72; P < .0001) and allergic rhinitis (OR, 1.94; 95% CI, 1.39-2.70; P < .0001). They also noted that children with AD were likely to have seen more providers than those without AD (2.3 vs 2.1; P = .003) and had a longer duration of dermatitis before patch testing (4.1 years vs 1.6 years; P < .0001).

The researchers acknowledged their study’s limitations, one being misclassification bias as patch testing interpretation is subjective, which could have affected the results. Also, the analyzed cohort mainly consisted of White girls, meaning the results may not be generalizable to other populations. Despite these limitations, the researchers noted that their findings support “the importance of referring children with AD for patch testing to consider ACD as an important comorbidity.”

“The results of this study underscore the need for children with AD to be referred to a specialist for evaluation of ACD,” the authors concluded. “Uncovering potentially relevant contact allergens can lead to improvement in quality of life, can decrease use of topical steroids and systemic immunosuppressants, and can significantly lessen overall disease severity.”

Reference

Johnson H, Aquino M, Snyder A, et al. Prevalence of allergic contact dermatitis in children with and without atopic dermatitis: a multicenter retrospective case-control study. J Am Acad Dermatol. doi:10.1016/j.jaad.2023.06.048