MINNEAPOLIS – When it comes to allergic contact dermatitis in children, the answer is sometimes hiding in plain sight. Cleansers, moisturizers, shampoos, detergents – all can contain ingredients that provoke significant reactions, yet many of these ingredients are not on the most common testing panels.
Erin Warshaw, MD, professor of dermatology at the University of Minnesota, reviewed common but often unsuspected causes of allergic dermatitis in the pediatric population at the annual meeting of the Society for Pediatric Dermatology.
Dr. Erin Warshaw
Even some hypoallergenic and frequently recommended products can contain preservatives and other ingredients that provoke allergic reactions, according to Dr. Warshaw. A chief culprit is methylisothiazolinone (MI), a preservative that came into common use as formaldehyde has been gradually phased out.
“If there’s anything I could emphasize from this talk, it’s MI, MI, MI. This is the major epidemic of our time in the contact dermatitis world,” Dr. Warshaw said. Upcoming publications, she added, will place MI in the top five most common contact allergens. “MI is in everything, including things you would think would be hypoallergenic,” she said. She recommended looking at ingredient labels with a keen eye when making testing decisions.
Despite MI’s status as a frequent culprit, it’s not an allergen that appears on common test kits, Dr. Warshaw pointed out. For example, it’s absent from one of the most commonly used test kits, the Thin-Layer Rapid Use Epicutaneous Patch (T.R.U.E. test).
The T.R.U.E. test, said Dr. Warshaw, has reasonable sensitivity – it can detect 71% of relevant positive patch tests (RPPTs) in children. However, she added, a recent study showed that about 23% of children reacted to a supplemental allergen. “That’s significant. One quarter of these individuals only reacted to a preservative … or a sunscreen, or an acrylate. These aren’t on the T.R.U.E. test.”
Decyl glucoside is another frequent culprit that is not included in commercial patch test kits. “It’s really an important emerging allergen,” said Dr. Warshaw, noting that it commonly cross-reacts with coco and lauryl glucoside, frequently found in fragrance-free products. “It’s always humbling when we find the allergen in the product we’ve recommended to our patients.”
Other important allergens not on the T.R.U.E. test include propolis, tocopherol, oxybenzone, and many surfactants and botanicals.
In order to avoid a confounding reaction to aluminum, Dr. Warshaw recommends testing using plastic-backed test chambers, such as IQ chambers, rather than Finn chambers, which are aluminum backed.
When working with families to track down allergens in the pediatric population, Dr. Warshaw adjusts her approach from what she would use for adults.
“What do I do differently in kids? First of all, I set expectations for children and parents,” she said. Some of the most frequent parental questions deal with food allergies, so she allots time to explain the rationale for not testing for food allergens when allergic contact dermatitis is suspected.
For many patients, “I try and frame that there is probably baseline eczema, and our goal is to try to figure out if there is an allergy in addition to that that is contributing to the flares,” she said. She makes sure to convey that “all it takes is one exposure every 3 weeks; that will keep this reaction going.”
However, she’s judicious in interpreting equivocal results. “I feel a responsibility not to label children with an allergy” if results are unclear. Finally, providing enough time is key, said Dr. Warshaw, who allots an hour for reviewing final testing results.
The take-home points? It’s worthwhile to patch test children, since over half of children will have at least one RPPT. Also, contact dermatitis can be an overlay on preexisting allergic dermatitis, so patch testing can still be helpful for these children. Supplemental allergens are important in patch testing, “especially in children with a negative test to a screening series,” Dr. Warshaw said.
She recommended accessing the Contact Allergen Management Program (CAMP) database, found on the American Contact Dermatitis Society website. The list is a searchable database that generates a list of “safe” products that don’t contain a given allergen. This resource is available for society members, but a member’s access code can be shared among faculty members at academic institutions, she said. Patients can also be given unique codes that will give them access for life, so they can use the CAMP database on a computer or via a smartphone app.
Dr. Warshaw reported no relevant financial disclosures.