The prevalence of allergic diseases has increased significantly in Western countries in the last decades. This increase is often explained by the loss of rural living conditions and associated changes in diet and lifestyle. In line with this 'hygiene hypothesis', several epidemiological studies have shown that growing up on a farm lowers the risk of developing allergic diseases. The consumption of raw, unprocessed, cow's milk seems to be one of the factors contributing to this protective effect. Recent evidence indeed shows an inverse relation between raw cow's milk consumption and the development of
asthma and
allergies. However, the consumption of raw milk is not recommended due to the possible contamination with pathogens. Cow's milk used for commercial purposes is therefore processed, but this milk processing is shown to abolish the
allergy-protective effects of raw milk. This emphasizes the importance of understanding the components and mechanisms underlying the
allergy-protective capacity of raw cow's milk. Only then, ways to produce a safe and protective milk can be developed. Since mainly heat treatment is shown to abolish the
allergy-protective effects of raw cow's milk, the heat-sensitive
whey protein fraction of raw milk is an often-mentioned source of the protective components. In this review, several of these
whey proteins, their potential contribution to the
allergy-protective effects of raw cow's milk and the consequences of heat treatment will be discussed. A better understanding of these bioactive
whey proteins might eventually contribute to the development of new nutritional approaches for
allergy management.