Development of food allergies with special reference to cow's milk allergy

Using strict criteria, the incidence of cow's milk sensitivity is probably 1% to 2% during the first 2 years of life. Although there is a wide spectrum of sensitivity symptoms caused by cow's milk, two major groups of infants are discernible. One group consists of infants who react to small amounts of cow's milk within a few minutes up to one hour, usually with gastrointestinal symptoms or urticaria. These infants are often atopic and have positive findings on skin prick tests and radioallergosorbent test (RAST) reactions to cow's milk allergens. The other group consists of children whose reaction to cow's milk occurs one hour or longer after intake of cow's milk or cow's milk-based formula. These reactions are usually not immunoglobulin (Ig)E-mediated and different immune and nonimmune mechanisms probably cause the symptoms. The risk of developing cow's milk sensitivity seems to be influenced by the atopic constitution of the infant and the age at which cow's milk is introduced. Early exposure to cow's milk increases the risk, not only of adverse reactions to this milk but also of developing allergies to other foods. It is suggested that early introduction of cow's milk may enhance the risk of future respiratory allergies. Allergists are still not in agreement as to whether the weaning process should be rapid or should consist of a gradual change from breast milk to cow's milk in order to minimize the risk of cow's milk allergy.