Combined skin prick and patch testing enhances identification of food allergy in infants with atopic dermatitis

Background: Early recognition of dietary allergies in infants with atopic dermatitis is essential for avoidance of unnecessary elimination diets, amelioration of the skin disease, and secondary prevention of the development of multiple food allergies. Simple and accurate methods of identifying provocative foods are urgently needed. Methods: The usefulness of skin prick and patch tests as indicators of cow milk allergy was evaluated in 183 patients ranging in age from 2 to 36 months with double-blind placebo-controlled (n = 118) or open (n = 65) cow milk challenges. Results: The oral cow milk challenges were interpreted as positive in 54% of both challenge types. Positive challenge rapidly elicited pruritus, urticaria, and/or exanthema in 49% of cases and delayed-onset eczematous lesions in 51%. The skin prick and parch tests gave markedly discrepant results; prick tests were positive in 67% of the cases with acute-onset reactions to milk challenge, whereas parch rests tended to be negative. Parch tests were positive in 89% of those with delayed-onset reactions, although prick rests were frequently negative. Conclusions: The observations indicate that IgE and T cell-mediated responses to cow milk can be distinguished in atopic dermatitis. Parallel skin testing with combined prick and patch tests can significantly enhance the accuracy in diagnosis of specific dietary allergies in patients with atopic dermatitis.