Top allergens
The top 10 allergens between children with and without AD were largely similar, the authors of the study report. Nickel was the most common allergen identified in both groups, and cobalt was in the top five for both groups. Fragrances (including hydroperoxides of linalool), preservatives (including methylisothiazolinone [MI]), and neomycin ranked in the top 10 in both groups, though prevalence differed.
MI, a preservative frequently used in personal care products and in other products like school glue and paint, was the second most common allergen identified in children with AD. Allergy to MI has “recently become an epidemic in the United States, with rapidly increasing prevalence and importance as a source of ACD among both children and adults,” the authors note.
Children with AD were significantly more likely, however, to have ACD to bacitracin (OR, 3.23; P = .030) and to cocamidopropyl betaine (OR, 3.69; P = .0007), the latter of which is a popular surfactant used in “baby” and “gentle” skincare products. This is unsurprising, given that children with AD are “more often exposed to a myriad of topical treatments,” Dr. Yu and his colleagues write.
Although not a top 10 allergen for either group, ACD to “carba mix,” a combination of three chemicals used to make medical adhesives and other rubber products (such as pacifiers, toys, school supplies, and rubber gloves) was significantly more common in children with AD than in those without (OR, 3.36; P = .025).
Among other findings from the study: Children with AD were more likely to have a longer history of dermatitis (4.1 vs. 1.6 years, P < .0001) prior to patch testing. Testing occurred at a mean age of 11 and 12.3 years for children with and without AD, respectively.
The number of allergens tested and the patch testing series chosen per patient were “not statistically different” between the children with and without AD, the researchers report.
Patch testing availability
Clinicians may be hesitant to subject a child to patch testing, but the process is well tolerated in most children, Dr. Perryman said. She uses a modified panel for children that omits less relevant allergens and usually limits patch testing to age 2 years or older due to a young child’s smaller surface area.
Dr. Yu, who developed an interest in patch testing during his residency at the Medical College of Wisconsin, Milwaukee, where he worked with a patch-testing expert, will test children as young as 3-4 months with a “small selection of patches.”
The challenge with a call for more patch testing is a shortage of trained physicians. “In all of Boston, where we have hundreds of dermatologists, there are only about four of us who really do patch testing. My wait time is about 6 months,” said Dr. Yu, who is also an assistant professor at Harvard Medical School, Boston.
Allergists at Massachusetts General Hospital do “some patch testing ... but they refer a lot of the most complicated cases to me,” he said, noting that patch testing and management of ACD involves detailed counseling for patients about avoidance of allergens. “Overall dermatologists represent the largest group of doctors who have proficiency in patch testing, and there just aren’t many of us.”
Dr. Perryman also said that patch testing is often performed by dermatologists who specialize in treating ACD and AD, though there seems to be “regional variance” in the level of involvement of dermatologists and allergists in patch testing.
Not all residency programs have hands-on patch testing opportunities, Dr. Yu said. A study published in Dermatitis, which he co-authored, showed that in 2020, 47.5% of dermatology residency programs had formal patch testing rotations. This represented improvement but is still not enough, he said.
The American Contact Dermatitis Society offers patch-testing mentorship programs, and the American Academy of Dermatology has recently begun offered a patch testing workshop at its annual meetings, said Dr. Yu, who received 4 weeks of training in the Society’s mentorship program and is now involved in the American Academy of Dermatology’s workshops and as a trainer/lecturer at the Contact Dermatitis Institute.
The study was supported by the Dermatology Foundation. Dr. Yu and his co-investigators reported no conflicts of interest. Dr. Perryman had no disclosures.
A version of this article first appeared on Medscape.com.