Allergic reactions to food
Posted by admin on June 15th, 2009
In the practice setting, an open or single-blind oral food challenge may be used to screen for allergic reactions to food. However, in cases in which multiple food allergies are diagnosed, positive responses should be confirmed by double-blind, placebo-controlled food challenges (DBPCFCs). DBPCFCs are the gold standard for diagnosing food allergies and have been used successfully in both children and adults for examining a variety of food-related complaints. The choice of foods used in DBPCFCs is based on history, skin test (or serum IgE antibody) results, or foods suspected on the basis of elimination diets. DBPCFC testing should be performed by a specialist or an experienced clinician; it is not a procedure suited for most primary care practices. (For details see Bock 1988 in Suggested Readings.)
Diagnosis of nonIgE-mediated food hypersensitivity such as malabsorption syndromes and eosinophilic gastroenteritis is facilitated by endoscopy and intestinal biopsy prior to and after the child is placed on an elimination diet. In the malabsorption syndromes, villous atrophy may be partial or complete and often is patchy. Consequently, multiple biopsies may be required to exclude this diagnosis, especially in young children. IgA antigliadin and IgA antiendomysial antibodies can be measured to screen for celiac disease.
However, this diagnosis depends on demonstrating biopsy evidence of villous atrophy and inflammatory infiltrate while the patient is ingesting gluten, resolution of biopsy findings after 6 to 12 weeks of gluten elimination, and recurrence of biopsy changes following reinstitution of gluten.
Food-induced enterocolitis and colitis syndromes may require an oral food challenge in the office or hospital. A positive challenge will provoke occult or grossly apparent blood in the stools, an increase in stool neutrophils and eosinophils over baseline, and an increase in the total peripheral blood neutrophil count of 3500 cells/mm³ over baseline at 6 to 8 hours after the challenge.
Tags: allergic diseases, allergy, food allergy