Dictionary of Allergies .. Childhood food allergies

Food allergy (FA) means an immunologic reaction resulting from the ingestion of food or food additives. An IgE or a non IgE mechanism can be involved. Food intolerance is a non immunologically mediated response. It can result either from a pharmacological or a metabolic mechanism or from contamination with micro-organisms. The incidence of FA in infancy and childhood is unknown and varies from one part of the world to another, depending on the type of food eaten in a particular country. In industrialized countries, the number of children suffering from FA is estimated to average 5%. About 10% of the atopic population develop clinical food allergy symptoms. In case of atopic dermatitis or children with bronchial asthma, the incidence is 25%.

The most common food responsible in infants and children are: cow's milk, egg, fish, corn, soy-bean, nuts, peanuts, some vegetables and fruit. Physiological and immunological processes serve to limit the amount of intact antigenic material which may penetrate the intestinal mucosa and gain access to immuno-competent cells or evoke immunological reaction. Enzymatic digestion degrades proteins in food to non antigenic fragments almost completely, but some intact proteins or antigenic derivatives can pass through the mucosa and stimulate immune responses at all ages. Allergic symptoms may appear after a few minutes (early reaction), after hours (delayed reaction), or after a few days (late reaction).

The most common cutaneous symptoms are itching, erythema, paleness, urticaria, local swelling, anaphylaxis and atopic dermatitis. Gastrointestinal symptoms include colic, nausea, vomiting, and diarrhea. In the respiratory tract, rhino-conjunctivitis, laryngitis, and bronchial illnesses, such as wheezing and coughing may occur. Increased levels of specific IgE are generally found in the early reaction type. Symptoms of the delayed reaction type are seldom accompanied by IgE mediated sensitivity.

Diagnosis is based on the current symptoms and the anamnesis. Diagnostic in vivo and in vitro methods are employed to help identify the pathogenic nutrient.MIUIn vivo: skin prick-tests, elimination diet (two weeks) followed by oral provocation test. MIUIn vitro: intestinal permeability test, using two inert sugars (lactulose and mannitol) is recommended. Test is carried out in two occasions: at fast, after a period of restricted diet and provocation test with the offending food. Food specific IgE antibodies and other IgE antibodies may be identified through radioimmunoassay (RIA) or enzyme immunoassay (EIA). At the present time, the prevention of IgE or non-IgE mediated

FA might be limited to the following possibilities: 1. avoidance of potentially allergenic food during the last trimester of pregnancy and during lactation in infants at risk. 2. Encouragement of breast feeding. Use of pharmacological agents when food allergy is present.

Higher antioxidant nutritional status reduces the risk of atopic dermatitis  and that such risk-reduction effects depend on nutrient type.

References

1. Molkhou, P.: Childhood food allergies. Satellite Symposium: Management of the Allergic Child and Adolescent. Schering-Plough Int. XVth Congress of the EAACI, May 12, Paris 1992.

2. Yunginger, J.W.: Lethal Food Allergy in Children. N. Engl. J. Med. 1992:327(6):421-22.

3. Oh SY, Chung J, Kim MK, Kwon SO, Cho BH. Antioxidant nutrient intakes and corresponding biomarkers associated with the risk of atopic dermatitis in young children. Eur J Clin Nutr. 2010 Jan 27.