July 23, 2015
Written by Sarah L Chamlin MD and Lisa Y Shen MD
41st Annual Meeting of the Society for Pediatric Dermatology
Boston, MA; July 9-12, 2015
Speaker: John Lee (Boston Children’s Hospital)
Clinical Director of the Food Allergy Program
There has been a longstanding association between atopic dermatitis (AD) and food allergies. This topic often arises when seeing young children with AD and is a challenging discussion for both physicians and parents. Many parents want to remove the food allergens from their child’s diet and cure the AD, but the relationship between dermatitis and allergies is much more complex.
Dr. John Lee reviewed this topic and offered some practical suggestions for dermatologists. Of note, food allergens are most relevant in infants with moderate to severe atopic dermatitis, and skin testing and specific IgE levels are useful diagnostic tools when used in the appropriate clinical settings (ie, when there is a history of possible reactions to food or refractory, severe AD, particularly exudative facial dermatitis in infants). Tests should be interpreted prudently for the parents as the degree of test positivity (wheal size, IgE level) predicts probability but not necessarily the severity of allergic reactions. Specific IgE (RAST) tests have a high negative predictive value; this is a great tool to rule out potential food allergies. Children with early-onset severe AD have the greatest risk for positive IgE testing to foods.
Among foods that have been implicated in refractory, moderate to severe AD, egg is the most common trigger. In infants with moderate to severe AD, 80% have strong positive skin tests to egg. Accordingly, egg elimination in patients with positive RAST testing has been shown to improve severity scores. In contrast, milk elimination seems to be overprescribed for AD, and only 2% of children with atopic dermatitis have a clinically relevant milk allergy.
Broad food panels should be avoided, and instead we should focus on major allergens, particularly egg, and, to a lesser extent, milk, peanut, wheat, and soy. It is important to note that food challenges are often successful (89%) when performed in the absence of prior suspected reactions.
Most notably, early introduction of certain foods (such as peanut) may actually decrease the incidence of food allergies. Israel, where peanuts are introduced prior to 12 months of age, has a very low incidence of peanut allergy (<0.04%). There is no evidence for delaying the introduction of allergenic foods, with the exception of peanut allergy in a sibling. Elimination diets may result in loss of tolerance, negative emotional and social effects, and nutritional deficiencies.
While few dermatologists order and interpret allergy testing, testing can be considered when infants have severe atopic dermatitis with exudative unrelenting facial involvement that is refractory to standard treatments, particularly if they have a history of a reaction to food. Children with mild to moderate AD should only be tested for food allergy if there is a history of foods triggering acute allergic symptoms such as lip swelling, urticaria, nausea, or wheezing. For those children, the focus should be on skin care (repair of the barrier to lessen the chance of IgE sensitization). Of note, treatment of atopic dermatitis and symptom improvement can actually alleviate parental concerns of allergies.