CLINICAL REACTIVITY TO BEEF IN CHILDREN ALLERGIC TO COWS MILK

Background: Cow's milk is one of the most common food allergens in chi ldren. Limited Information is available on the prevalence of reactivit y to a related food source, beef. The purposes of this study were to e xamine the prevalence of symptomatic sensitivity to beef in a selected pediatric population and to determine the frequency of concomitant re activity to cow's milk and beef. Methods: Children referred for assess ment of atopic dermatitis and possible food hypersensitivity were eval uated for symptomatic reactivity to beef by double-blind placebo-contr olled food challenges (DBPCFCs) and subsequent open feedings of beef. Sodium dodecyl-sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), immunoblot, and immunodot blot analyses were performed with patients' sera on preparations of beef extracts subjected to different cooking c onditions: raw (no heating), medium, and well-cooked. Results: Eleven of 335 children referred for evaluation of atopic dermatitis and possi ble food hypersensitivity were found to have symptomatic sensitivity t o beef; eight were also sensitive to milk, as demonstrated in previous DBPCFCs. Eight patients reacted to beef during DBPCFC, and three tole rated beef in a DBPCFC and well-cooked beef in an open challenge but r eacted to ingestion of less well-cooked beef. SDS-PAGE of raw beef rev ealed at least 24 protein fractions. Several protein bands in raw beef appeared to denature with heating. Bovine serum albumin and bovine ga mma globulin were heat-labile in the beef extract, but six protein fra ctions persisted even after heating the beef extract for 2 hours at 85 degrees C. IgE from patients reacting to rare and well-cooked beef bo und up to six of these heat-resistant fractions, but IgE from patients reacting only to rare beef failed to bind any of these fractions with one exception. in addition, patients reacting to rare and well-cooked beef had specific IgE to a 17.8 kd fraction, which was only weakly re cognized by one patient reacting only to rare beef. Conclusions: Speci fic IgE antibodies to heat-labile beef proteins might explain why some patients can tolerate well-cooked beef but not medium-rare and rare b eef. Patients reacting only to rare beef may not need to maintain a co mplete beef elimination diet.