Dermatologists Caution that Eczema May Be Precursor to Food Allergies
Eczema, or atopic dermatitis, affects about 10 to 20% of children worldwide, with about half of those being diagnosed before the age of one. Doctors have believed that food allergies are one of the triggers of the red, itchy rash but new research may indicate that eczema may actually be a precursor to food allergies instead of a consequence.
Eczema Can Precede Diagnosis of Food Allergy
Atopic eczema is due to a hypersensitivity reaction in the skin. This can lead to long-term inflammation. Food allergies are similar reactions, in that a certain trigger can cause an exaggerated immune system response, causing production of a substance called immunoglobulin E, or IgE.
Dermatologist Jon M. Hanifin MD FAAD, a professor of dermatology at Oregon Health and Science University presented a five-year multi-center study last week at the 69th Annual Meeting of the American Academy of Dermatology. In a group of children aged three to 18 months that had even a mild case of atopic dermatitis, roughly 15 percent also were affected by food allergies.
In addition, those with more severe cases of atopic dermatitis generally have a higher incidence of developing food allergies. Dr. Hanifin notes that patients with eczema make larger amounts of IgE than any other group of patients. Recent research indicates that chronic atopic dermatitis causes defects in the skin’s protective outer layer (the epidermis) which then allows irritants, microbes, and allergens to penetrate the skin. Therefore, the more the skin is compromised, the greater the risk of allergic reactions.
“In most cases, patients experience atopic dermatitis before food allergies,” says Dr. Hanifin, “so it is important for parents of infants and small children affected by this skin condition to be aware of the risk of food allergies.”
About one-third of eczema patients respond to food triggers. Those most common to both eczema and food allergies are eggs, milk, peanuts, soy and wheat.
Although skin testing can be difficult when a child has eczema, proper testing for a food allergy is critical. According to the new guidelines set by the American College of Allergy, Asthma and Immunology (ACAAI), it is recommended that “children less than 5 years old with moderate to severe atopic dermatitis be considered for food allergy evaluation” especially if the child has persistent eczema despite optimized therapies and there is a reliable history of immediate reaction after ingestion of a specific food.
A food challenge test is considered the most definitive method for identifying a true food allergy versus insensitivity to a certain ingredient. These tests should only be conducted in a doctor’s office so immediate medical attention is available should the child have a severe reaction.
A RAST test, or radioallergosorbent test, is a type of blood test that can be used in combination with skin tests or be used in situations where food challenge tests are risky. Unfortunately, RAST tests are more expense and not considered as accurate as other food allergy tests.
Updated March 29, 2017