Cow's milk protein allergy is defined as an immunological reaction to one or more milk proteins. A variety of symptoms can be suggestive for cow's milk protein allergy . Cow's milk protein allergy is suspected clinically in 5-15% of infants, while most estimates of prevalence of cow's milk protein allergy vary from only 2 to 5 %. Confusion regarding cow's milk protein allergy prevalence is often due to differences in study populations, study design and a lack of defined diagnostic criteria. The importance of defined diagnostic criteria needs to be emphasised. It precludes infants from an unnecessary diet and avoids delay in diagnosis, which can lead to malnutrition.