Allergic contact dermatitis: Pediatric patch tests mirror those of adults

National Report - Children with allergic contact dermatitis frequently react to the same allergens as adults with this condition do, according to a recent multi-center study conducted at the University of Miami and the University of Pennsylvania that calls for increased patch testing in children, especially those with chronic dermatitis.

Sharon E. Jacob, M.D., says that when she opened the University of Miami Department of Dermatology's patch test clinic in 2004, "A significant portion of my practice was pediatrics."

However, she says that when she searched medical literature for U.S. studies addressing patch testing in affected pediatric patients, "There was no U.S.-based literature at that time. So, we decided to follow what we did, retrospectively review our data and report our findings."

Dr. Jacob is currently assistant professor of medicine and pediatrics at the University of California, San Diego, where she practices patch testing at Rady Children's Hospital.

Clinical study

The multi-center study included 65 symptomatic children (35 girls, 30 boys) from ages one to 18 years who had undergone patch testing between May 2001 and May 2006 at either of the two referral centers.

Patients' diagnoses included deteriorating atopic dermatitis and localized recalcitrant dermatitis. Researchers tested all but two patients over age 8 with the North American Contact Dermatitis Group Standard series of allergens, as well as with selected supplemental allergens and each patient's own personal care products and medicines.

Investigators used standard allergens (Chemotechnique Diagnostics) applied to Finn Chambers (Allerderm) for patients tested at the University of Pennsylvania and IQ chambers (Chemotechnique Diagnostics) for patients tested at the University of Miami.

Researchers taped tests with Hypafix (Smith & Nephew Inc.) to clinically normal skin on patients' backs for 48 hours and read the tests at 48 and 96 hours. Patients ages five years and younger were read at 48, 72 and 96 hours.

"We tested a group of children, determined what they were allergic to and removed those chemicals and their sources from their environments," Dr. Jacob explains.

Relevance

If patients got better after the chemicals were removed, investigators judged the allergens to be clinically relevant. In this regard, investigators assigned the following grades of clinical relevance:

Definite - if the allergen was present in the patient's environment, the dermatitis corresponded to point(s) of contact with the allergen and the dermatitis significantly improved when the allergen was removed, or recurred with re-challenge

• Probable - if the case met the above criteria but no follow-up information regarding improvement status or re-challenge results was available

• Possible - if the case met only one of the "definite" criteria

• Past - if the allergen was found in the child's past environment

• Unlikely - if researchers could not find the allergen in the child's current or past environment

"The amazing thing that we found was that a significant number of the top allergens in children were the same" as the top allergens that plague U.S. adults, Dr. Jacob says.

Top allergens

For example, as in adults, "Nickel was the top allergen (with 11 children having definite or probable clinical relevance). And we found that U.S. children affected with contact dermatitis were as likely to have relevant positive patch tests as were adults, which hadn't been shown before," Dr. Jacob says.

Therefore, she says, children could be tested in the same manner that adults are tested, "and if they were tested properly and clinically relevant allergens identified, then we could get them better."

The second-most-frequent metal to which children were allergic was cobalt. Dr. Jacob says that five of the seven patients who were allergic to cobalt also showed sensitivity to nickel. Sources of exposure to these metals included orthodontic braces, coins, school chairs and ballet balance bars.

Researchers found thimerosal to be the second most prevalent allergen overall, but it had very low clinical relevance. For all 10 children who reacted positively to thimerosal, investigators considered its clinical relevance unlikely.

Positive reactions to this allergen probably occurred secondary to vaccine exposure, which is expected to decline over time as fewer vaccines are being preserved with this agent, Dr. Jacob says.

Myroxylon pereirae (balsam of Peru) ranked as the third most prevalent allergen, with nine children showing definite or probable clinical relevance.

It is a complex botanical mixture used as a screen for fragrance contact dermatitis. Notably, it (or cross-reacting chemical constituents) can be found in body washes, shampoos and diaper balms, Dr. Jacob says.

Treatment

The study's findings suggest that if one is treating a child with chronic, recalcitrant dermatitis, "Patch testing would be warranted to see if there's an environmental chemical that's causing the problem. We found it to be a very useful tool" in such cases, she says.

Researchers also found that many of their patients had been prescribed potent medications such as cyclosporine or systemic steroids to treat symptoms of their allergies.

"By finding the chemical they were allergic to and removing it, we were able to get them off these systemic immunosuppressive medications, get them back to school and give their families their lives back," she says.

Study weakness

One potential weakness of the study is its relatively small pilot population (low power), Dr. Jacob says.

However, she says that nationally, the total reported number of children patch tested in the past five to 10 years is less than 1,000.

"We're dealing with a population that is underserved. Most dermatologists are not patch testing children," she says, perhaps at least partly because the Thin-layer Rapid Use Epicutaneous (T.R.U.E. Test, Allerderm) is approved only in patients aged 18 years and older.

"Most children with chronic dermatitis are being symptomatically managed with intensive topical regimens, ultraviolet therapies, prednisone, cyclosporine and other systemic medications rather than being patch tested to learn the source of their allergies," Dr. Jacob adds.

However, she says she and her colleagues are among researchers attempting to prove that the T.R.U.E. Test is safe in children as well. The 100-patient study was expected to be completed this summer. DT

Disclosure: Dr. Jacob reports no relevant financial interests at the time the pilot study was conducted. Since then, however, she has become an investigator for Allerderm.