In the past, positive blood and skin tests would often be mistaken for a food allergy because they would indicate the presence of immunoglobulin E antibodies, but it is important to remember that these are typically higher in patients with atopic dermatitis, according to a speaker at the 69th Annual American Academy of Dermatology Meeting conducted in New Orleans this week. “Those antibodies are not diagnostic, and the only way to diagnose food allergy is with a strong history of reactions or a challenge,” Jon M. Hanifin, MD, of Oregon Health & Science University, said in a press release. “This is done in a doctor’s office, using small increments of the food in question and increasing the amount until an allergic reaction occurs or does not occur. Usually a parent can pinpoint if a child has a true food allergy because the allergic reaction will appear so quickly with lip swelling or hives, quite distinct from simply food intolerance.”
Between 6% and 10% of children have atopic dermatitis, and about one-third of these children have food allergy. Recent research examining the genetic basis of atopic dermatitis has shown that this chronic skin condition is likely related to a defect in the epidermal barrier, which allows irritants, microbes and allergens (such as food) to penetrate the skin and cause adverse reactions. Because 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.
New guidelines recently issued by the National Institute of Allergy and Infectious Diseases established a protocol for the proper evaluation and management of food allergy. The guidelines recommend that children who are younger than aged 5 years with moderate to severe atopic dermatitis be considered for food allergy evaluation if they have persistent atopic dermatitis despite optimized management or if the child has a reliable history of an immediate reaction after eating a specific food.
Hanifin said research is also ongoing into whether withholding foods is leading to more allergies than an unrestricted diet in young children. This may provide future insight in potential ways to prevent food allergies. He said children in Israel seldom get peanut allergy, which may potentially be attributed to the use of peanut proteins in pacifiers in that country. In the United States and Europe, where peanut allergies are more common, infants are not usually exposed to this food until they are toddlers – the time when most peanut allergies are noticed.
“There is some thinking that withholding foods might actually be causing more allergies, and that an unrestricted diet may help tolerize babies to foods that could potentially cause a problem later in life,” Hanifin said. “Ongoing studies in this country using oral immunotherapy appear promising, and physicians hope that we may discover how to prevent food allergies in the future while continuing to provide successful treatment for children with atopic dermatitis.”
Source: Hanifin J. Food allergy and dermatology. Presented at: The American Academy of Dermatology 69th Annual Meeting; Feb. 4-8, 2011; New OrleansMore