Conference Coverage

Patch testing in atopic dermatitis: when and how



– The prevalence of allergic contact dermatitis is elevated among patients with atopic dermatitis – and it pays to know their major sources of risk, according to Jonathan I. Silverberg, MD, PhD.

photorobot/Getty Images

“What are atopic dermatitis patients allergic to? It’s all coming from their personal care products and the things being used to treat their atopic dermatitis,” Dr. Silverberg said at the Hawaii Dermatology Seminar provided by the Global Academy for Medical Education/Skin Disease Education Foundation.

Dr. Silverberg, of the department of dermatology at Northwestern University, Chicago, coauthored a systematic review and meta-analysis that examined the association between AD and contact sensitization. In their examination of 74 published studies, the investigators found that the likelihood of allergic contact dermatitis was 1.5-fold greater in adults and children with AD than in healthy individuals from the general population (J Am Acad Dermatol. 2017 Jul;77[1]:70-8).

This finding is at odds with an earlier widespread belief that AD patients should not be at increased risk because the immune profile of their primarily Th2-mediated disease would have a suppressant effect on Th1-mediated hypersensitivity.

“Recent data are calling into question old dogmas and reshaping the way we think about this. And this is not just an academic exercise, this is highly clinically relevant,” the dermatologist asserted.

The results of the meta-analysis prompted Dr. Silverberg and colleagues to conduct a retrospective study of more than 500 adults patch tested to an expanded allergen series at Northwestern’s patch test clinic with the purpose of identifying the common offending allergens in patients with AD. The key finding: The patients with AD were significantly more likely to have positive patch test reactions to ingredients in their repetitively used personal care products, topical corticosteroids, and topical antibiotics than the individuals without AD. The probable explanation for this results is that the skin barrier disruption inherent in AD allows for easier passage of weak allergens through the skin (J Am Acad Dermatol. 2018 Dec;79[6]:1028-33.e6).

Dr. Jonathan I. Silverberg, Northwestern University, Chicago Bruce Jancin/MDedge News

Dr. Jonathan I. Silverberg

Lanolin was identified as a particularly common allergen in the AD group. “Lanolin is found in one of the most commonly used moisturizers we recommend to patients: Aquaphor. It’s also found in tons of lip balms and emollients. Pretty much every soft soap out there contains lanolin, and it’s in a variety of other personal care products,” Dr. Silverberg noted.

Other common offenders in the AD population included fragrance mix II, cinnamal, quaternium-15, budesonide, tixocortol, carba mix, neomycin, bacitracin, rubber mix, and chlorhexidine. Relevance was established in more than 90% of the positive reactions.

“You can patch test them directly to their personal care products and make that connection beautifully and see how they’re reacting to them,” he said.

When to patch test atopic dermatitis patients

Dr. Silverberg was a coauthor of multidisciplinary expert consensus guidelines on when to consider patch testing in AD (Dermatitis. 2016 Jul-Aug;27[4]:186-92). “We had to go consensus because we don’t have nearly enough studies to provide true evidence-based recommendations,” he explained.

Because allergic contact dermatitis is a potentially curable comorbid condition in AD patients, it’s important to recognize the scenarios in which patch testing should be considered. These include AD refractory to topical therapy; adolescent- or adult-onset atopic dermatitis; and in AD patients with an atypical or evolving lesional distribution, such as localized dermatitis on the eyelids, head and neck, or hands and feet. Patch testing is also warranted before initiating systemic therapy for AD.

“If you’re about to put a patient on a biologic or phototherapy and step them up to a whole new class of risk of adverse events, that’s an ideal time to think about reversible options,” Dr. Silverberg advised.

Another situation in which he considers patch testing advisable, although this one isn’t covered in the consensus guidelines, is in AD patients with prominent nummular eczema lesions. “Widespread nummular eczema lesions may be a sign of allergic contact dermatitis in atopic dermatitis patients. I’m not saying everyone with nummular lesions is going to have a positive patch test, but it’s definitely a situation you want to think about,” he said.


Next Article: