By the end of the last century prevention of waterborne infections by chlorination of water supplies, pasteurization of cow's milk (CM) and production of suitable, easily cleaned bottles and nipples for infants had made artificial infant feeding a relatively safe procedure. But in the early years of the present century unexplained difficulties were reported in infants fed with cow's milk; some of them had continuous diarrhoea and failed to thrive (103). It was speculated that such infants had difficulty in digesting foreign proteins, although they could readily assimilate those in breast milk. In the following years cases of anaphylactic shock caused by CM were described, one of them with a fatal outcome (29). Animal studies showed that one species produced precipitins to proteins of milk from another species, and this type of reaction to the foreign structure of CM proteins was presumed to account for the symptoms seen in infants (29). In 1906, precipitins to CM were found in blood from a marasmic infant fed with CM (80). A year later reports appeared describing successful desensitization: injections of small quantities of cow serum cured and prevented hypersensitivity to oral CM and its symptoms (102). This was not a solution to the problem, however, as treatment with serum caused severe reactions (95). The mechanism and components of C M causing these reactions were debated. Wernstedt suggested that the symptoms were due to altered reactivity to CM because of earlier contact with it, and proposed that it should be called allergy (119). Subsequently, the intestinal symptoms were shown to be caused by the whey fraction of CM (42). They were noted to vary in severity and disappeared with increasing age. A decade later (1921) urticaria was described as a symptom of CM hypersensitivity (104). By the 1930's and 40's however, CMA was considered a rare disease ( I 12), but the decrease in breast feeding in most developed countries has made cow's milk allergy (CMA) an important cause of infant morbidity and one of the best known and most frequently encountered problems in current infant feeding practices.
DEFINITIONThe majority of infants can be reared on CM formulas without untoward effects. However, sensitive immunochemical methods show that they do react to the foreign proteins in CM. When the immunologic reactions to CM are associated with clinical symptoms, the child can be said to be allergic to CM (89). Obviously, the simplest and the most convincing way to verify cow's milk allergy (CMA) would be to demonstrate this either abnormally strong or qualitatively altered immune reaction to C M proteins. As yet, however, this cannot be done by any single test or combination of tests. Therefore the diagnosis of CMA has to be based on the clinical response to CM. In most cases it is enough to observe a favourable response to elimination of CM, reappearance of symptoms during one challenge test and their -disappearance on renewed elimination. When symptoms are severe it is unethical to perform more than one challenge.Ot...