Skin Test Using Sterile Tape Uncovers Food Sensitivity

Ingrid Hein

March 19, 2020

In young children with atopic dermatitis, cells from normal skin can predict sensitivity to food and aeroallergens, and the degree of sensitivity, according to research by a team from Cincinnati Children's Hospital Medical Center.

"The most striking finding is that we saw phenotypes in the nonlesional skin that are just like the lesional skin," said study lead Gurjit Khurana Hershey, MD, PhD. "From normal skin, we can predict how bad disease is and what they're going to be sensitized to."

"These findings could lead to a redefinition of the allergic march," which is now defined as a progression from atopic dermatitis, to food allergy, to allergic rhinitis and asthma, she told Medscape Medical News.

And food allergy could be present from the very start. "The atopic march only accounts for 3% of kids," said Hershey.

She and her colleagues found endotypes in nonlesional skin that correlate to aero- and food-allergy cosensitization after examining data from 400 children with atopic dermatitis who were enrolled, before they were 2 years of age, in the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (MPAACH) cohort.

The investigaators compared transdermal water loss, the expression of filaggrin and alarmin, and staphylococcal colonization in lesional and nonlesional skin cells collected, using sterile tape, from the study participants.

And they found that characteristics normally seen in lesional skin — high alarmin expression, low levels of filaggrin, and elevated colonization with Staphylococcus aureus — were also seen in nonlesional skin.

"This is the first time I'm aware of the detection of a subclinical sensitization pattern in normal skin," Hershey said.

The test might also reveal type of allergy and degree.

"We don't have a cutoff yet, but we see that the children with the lowest expression of filaggrin have food sensitization," she explained. "It was measured in all 400; we looked at absolute value and variable, and we found that as the value gets lower, the risk to food sensitization grows bigger."

Cosensitization appears to be a factor. "There's something about having food and aero sensitization together that's important," said Hershey. "We don't know if one is helping the other and getting through the skin, but we don't see aero sensitization alone."

The study participants were a median of 2.3 years of age when they were assessed. "Many had visually cleared their eczema, but we still saw lower filaggrin levels in the tape and we were able to detect higher transdermal water loss," said Jocelyn Biagani Myers, PhD, the study investigator scheduled to present the findings at the now-canceled American Academy of Allergy, Asthma and Immunology 2020 Meeting in Philadelphia.

With these findings, the MPAACH team has shifted enrollment to a younger age group so they can assess allergic development. "We are now recruiting babies at 4 months to look at what age we can predict allergy," Biagani Myers told Medscape Medical News.

The cohort has 570 participants, and 100 of these were enrolled before they were 12 months of age.

"The next step is to look at specific allergens," she said. The team hopes to find a way to identify which allergies will develop from normal skin samples.

Enrollment will likely expand to children without atopic dermatitis. "Nobody has ever looked at filaggrin levels in healthy kids," she said.

Skin Barrier Dysfunction Associated With Food Allergy

A unique subtype of eczema was recently reported in children with confirmed peanut allergy (skin prick test wheal, ≥8 mm).

In that study, normal skin samples were collected with sterile tape from 62 study participants, who were 4 to 17 years of age. Twenty-one had atopic dermatitis with food allergy, 19 had atopic dermatitis but no food allergy, and the 22 had no atopic dermatitis.

For children with atopic dermatitis and peanut allergy, S. aureus colonization was elevated, skin was more prone to water loss, and gene expression typical of an immature skin barrier was clearly associated with food allergy.

"We found those differences not within the skin rash but in samples of seemingly unaffected skin inches away," study lead Donald Leung, MD, PhD, from National Jewish Health in Denver, said in a press statement. "These insights may help us not only better understand atopic dermatitis, but also identify children most at risk for developing food allergies before they develop overt skin rash, and eventually, fine tune prevention strategies so fewer children are affected,"

"The fact that the normal skin had low filaggrin is not surprising," said Kelly Maples, MD, from Children's Hospital of the King's Daughters in Norfolk, Virginia. "But I do think the alarmin and the Staphylococcus aureus being elevated is significant that shows there is inflammation even if we can't see it."

However, early tape testing could lead to an overdiagnosis of food sensitivity or an increase in false positives. "Parents might unnecessarily avoid foods. We could end up creating allergy."

Challenges of Early Diagnosis

Already, "we spend more time telling people — convincing people — they don't have food allergy," Maples told Medscape Medical News.

It's important that patients with a compromised skin barrier don't cause further inflammation, she said.

"Eczema puts you at risk for food allergy because of impaired skin function; it's not food allergy causing eczema," she explained. There are allergens everywhere. "We even find peanut and egg in dust, and that gets through to the skin."

People with atopic dermatitis should avoid using soap and detergents and keep the skin moisturized. "As soon as you get out of the bath, use a thick emollient with ceramides to trap moisture and further protect the skin barrier," she said.

Still, many parents want to know where their children stand.

Food allergies are scary for parents, so knowing about the allergy early could prevent allergic events like anaphylaxis. "Even if we don't have a prevention strategy, we could test and institute prevention early if we know they have an allergy," said Hershey.

"We're hoping we'll be able to offer a test that doctors can do in their office," said Biagani Myers. "A physician would collect a skin sample with the tape and then send it to a lab for analysis."

"If there's a concern about food allergy, a food challenge can be done in the physician's office, instead of waiting for a reaction at home."

American Academy of Allergy, Asthma and Immunology (AAAAI) 2020 Meeting.

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