Atopic Dermatitis Is a Strong Precursor to Food Allergies

Takeaway points:

• There is growing evidence suggesting that atopic dermatitis is a precursor to allergic diseases rather than a consequence.
• However, despite the link between atopic dermatitis and food allergies, proper testing for a food allergy is critical in determining if an actual allergy exists.
• The new food allergy guidelines issued by the National Institute of Allergy and Infectious Diseases provide a clear definition of food allergy, and distinguish it from allergic sensitization to food.
• Children under the age of five with moderate to severe atopic dermatitis be considered for food allergy evaluation if the condition persists despite optimized management and topical therapy, or if he or she has a reliable history of an immediate reaction after ingestion of a specific food.

New guidelines from the NIAID identify which children should be considered for food allergies and emphasize the importance of proper diagnosis.

Increasing evidence indicates atopic dermatitis—one of the most common forms of eczema—is a precursor to allergic diseases rather than a consequence, according to data presented at the 69th Annual Meeting of the American Academy of Dermatology (AAD). As a result, dermatologists are advising parents of infants and young children affected by this common skin condition to be aware of the potential for future food allergies.

“Considering that six to 10 percent of children have atopic dermatitis and that up to one-third of those individuals may have documented food allergy, the number of these children affected by food allergies may be significant,” said Jon M. Hanifin, MD, of Oregon Health & Science University in Portland, in a AAD press release.

A five-year study conducted by Hanifin and others in infants age three to 18 months found that even in reported mild cases of atopic dermatitis, roughly 15% of infants had definite food allergies. They also found that patients with more severe cases of atopic dermatitis generally have a higher incidence of developing food allergies. However, despite the link between atopic dermatitis and food allergies, proper testing for a food allergy is critical in determining if an actual allergy exists.

The new food allergy guidelines issued by the National Institute of Allergy and Infectious Diseases clearly define a food allergy as an adverse health event that stems from an immunologic reaction upon exposure to a specific food. An allergic sensitization to food, on the other hand, is determined by the presence of specific IgE antibodies in the blood and confirmed by blood or skin tests. Patients with atopic dermatitis produce larger amounts of IgE than any other group of patients, making the relationship between food allergies and atopic dermatitis seem quite complex.

“As dermatologists, we have seen children with highly restrictive diets who might have more than 20 positive skin or blood tests. But we now know that a positive test is not an allergy unless it is confirmed by an actual food challenge,” said Hanifin. “In the meantime, children may be malnourished and experience a host of other problems by not having proper nutrients in their diets. The fact is that children may only have a sensitization to the foods, but are being treated as if they have food allergies. We’re hoping that these new guidelines will help clear up this misinformation and ensure a proper diagnosis.”

The  new guidelines recommended that “children less than 5 years old with moderate to severe atopic dermatitis be considered for food allergy evaluation for milk, egg, peanut, wheat and soy, if at least one of the following conditions are met:
The child has persistent atopic dermatitis in spite of optimized management and topical therapy.
The child has a reliable history of an immediate reaction after ingestion of a specific food.”

In the past, positive blood tests and skin tests may have been mistaken for a food allergy because they would indicate the presence of IgE antibodies, which are higher in patients with atopic dermatitis. Those antibiotics, however, are not indicative, according to Hanifin, who states that “the only way to diagnose food allergy is with a strong history of reactions or a challenge—where you feed patients the food indicated by tests and see if they have an immediate reaction.” This, he stated, is done “using small increments of the food in question and increasing the amount until an allergic reaction occurs or does not occur.”

Recent research examining the genetic basis of atopic dermatitis has shown that the condition is likely related to a defect in the skin's epidermal barrier, allowing irritants, microbes, and allergens to penetrate the skin and cause adverse reactions. Since the skin barrier in patients with atopic dermatitis is compromised and open to absorb proteins, it allows sensitization to certain foods, leading to a positive skin or blood test.

Ongoing studies using oral immunotherapy “appear promising, and dermatologists hope that we may discover how to prevent food allergies in the future while continuing to provide successful treatment for children with atopic dermatitis,” he noted.