LENGTH OF TOTAL BREAST-FEEDING AND THE CLINICAL PICTURE OF COW'S MILK ALLERGY

Abstract

238 Background Infants allergic to cow's milk with a delayed type reaction are usually younger than those with IgE-mediated, immediate type reaction. The age at introduction and the amount of ingested protein are shown to influence the subsequent immune reaction. We examined the effects of the length of breast-feeding and introduction of formula on the development of allergic reactions to cow's milk. Methods Infant feeding regimen was daily registered at hospital and at home for the first 8 weeks in a cohort of 6 209 healthy term infants, who were followed prospectively for symptoms of cow's milk allergy (CMA). 247 infants with symptoms suggestive of CMA recovered on a 2-4 weeks milk-free diet, and 118(48%) reacted positively to cow's milk in a challenge test. On day 1, cow's milk was given at hospital in quantities of 1, 10, 50 and 100ml at intervals of 30-60 min. Next day, infants without symptoms continued the challenge at home. All the patients were examined on day 5 to verify delayed symptoms, and a month later to confirm the negative challenge result. The challenge test was considered positive if one or more of the following symptoms appeared: urticaria, exanthema, atopic eczema, vomiting, diarrhoea, wheezing, allergic rhinitis or conjunctivitis. The CMA+ infants were grouped according to the length of total breast-feeding (mean 7.8 months, 95% CI 7.1-8.4) and lower and upper quartiles were selected for comparisons: group A less than 5.5 mo (n=31), group B at least 10 mo (n=38). Results In both groups, infants were similarly exposed to cow's milk at hospital (39% vs. 32%), but the median ages when cow's milk was introduced at home differed: 1.0 mo (group A) and 4.0 mo (group B; p<0.001). Before the elimination diet, 80% (group A) and 5% (group B) of the infants were given cow's milk daily (p<0.001). The first symptoms of CMA appeared at the mean ages of 1.7 mo (group A) and 3.3 mo (group B; p<0.001); in 23% and 34% of the patients during exclusive breast-feeding. The occurrence of urticaria (10% vs. 68%) and respiratory symptoms (48% vs. 21%) differed significantly between the groups. TableConclusions In this unselected group of CMA+ infants, frequent, early introduction of cow's milk induced the development of a non-IgE-mediated, delayed type hypersensitivity to cow's milk and enhanced the milk-specific IgA- and IgG-responses. In contrast, infants, who were mainly breast-fed and given cow's milk only occasionally, more frequently developed an IgE-mediated reaction to cow's milk and, also, more often showed other signs of atopy.