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Am Fam Physician. 2008;77(11):1598-1602

Background: Moderate to severe atopic eczema in infants is often associated with elevated serum immunoglobulin E (IgE) levels, food sensitization, and a family history of atopy. Previous studies report significant IgE food sensitization to cow's milk, eggs, or peanuts in children with moderate to severe atopic eczema. However, these study populations were often derived from patients referred to allergy departments. To avoid this referral bias, Hill and colleagues tested for IgE food sensitization in infants with eczema who presented to a dermatology clinic without previous food allergy evaluation.

The Study: Consecutive infants six to 12 months of age with moderately severe eczema were evaluated prospectively. Allergists performed skin-prick tests and measured serum IgE antibodies to cow's milk, egg, and peanut. IgE food sensitization was diagnosed if the skin-prick test wheal exceeded food-specific diameters for children younger than two years. Additionally, serum IgE levels for each of the three foods tested were considered positive if they exceeded the 95th percentile for positive predictive value already associated with challenge-proven food allergy. Values for children younger than two years were available for milk and egg, but data from older children had to be applied to determine values for peanut.

Results: Based on an assumption that 30 percent of infants presenting to the dermatology clinic would have IgE food sensitivity, 81 patients were required to adequately test the null hypothesis that there was no association between atopic eczema and IgE food sensitization. However, the prevalence found in the first 51 patients was so great that an interim analysis indicated that additional patients were unnecessary.

The mean onset of eczema was 12 weeks. Eighty-six percent of the infants were sensitive by skin-prick testing to at least one food and, of those, 50 percent were sensitive to more than one food. Sixteen percent were sensitive to cow's milk, 73 percent to egg, and 51 percent to peanut. Serum IgE testing showed significant concordance to skin-prick testing for cow's milk and egg in children younger than two years. However, there was significant discordance (i.e., lack of agreement) between serum IgE testing and skin-prick testing for egg and peanut in children older than two years.

Most of the infants were breastfed (94 percent), and 61 percent had no solid food or formula exposure before the onset of atopic eczema. More than one half were breastfed exclusively for at least four months, during which time the mothers were not on restricted diets. In total, 71 instances of IgE food sensitization occurred in 51 patients. In 60 of those instances, the infants had never knowingly been fed the particular food.

Conclusion: Consistent with other referral-and community-based studies, this study found that more than 80 percent of infants with moderately severe atopic eczema demonstrated evidence of IgE food sensitization. In 95 percent of cases, IgE food sensitivity is consistent with clinical allergy upon food challenge. The authors conclude that although a benefit of maternal low-allergen diet in breastfeeding has been described, the role of food allergy in eczema is unknown. They suggest that food allergy screening be included in the evaluation of moderate atopic eczema in infants six to 12 months of age.

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