Food allergies are more common in children with eczema, especially those with more severe eczema. Food allergies can sometimes be triggers of the disease, or more commonly, are just secondary problems associated with the eczema. In some patients, they may induce dermatitis and contribute to the severity of skin disease, while in others, urticaria (hives) or symptoms such as nasal congestion or wheezing may occur.
Food allergy testing can be performed with skin prick tests or with blood tests (for specific IgE). Unfortunately, positive blood tests only identify an allergy correctly 25 percent of the time, with many individuals having positive tests, but fortunately no true clinical allergy. Negative tests are rather reliable at telling someone they do not have a food allergy.
Certain individuals are recommended to undergo food allergy evaluation.
Patients with severe eczema may need to be hospitalized to control their eczema and be given suspected foods before ruling out the possibility of food allergy. In infants with food allergy who are being breastfed, the mother will need to restrict her diet to eliminate potential food allergens, which may be transferred through breast milk.
Removal of proven food allergens from the patient’s diet may lead to significant improvement. It is important for patients to completely avoid implicated foods, as even small amounts of the food allergen can contribute to food-specific IgE synthesis.
Potential food allergens can be identified by having the doctor take a careful history. If food allergens are suspected the doctor may perform selected allergy skin tests. Negative prick skin tests or serum tests for allergen-specific IgE have a high predictive value for ruling out suspected allergens. Positive skin or in vitro allergy tests, particularly to foods, often do not correlate with clinical symptoms and should be confirmed with controlled food challenges or elimination diets. As a rule, extensive elimination diets, which in some cases can be nutritionally deficient, are not necessary.