Milk is a primary source of nutrition for infants after the birth and also for human beings. Generally, milk is either from humans (women) or from cattle origin they contain various types of proteins, vitamins, minerals and so on. Components in milk show various beneficial actions in beings and some of the studies found that metabolites of it show severe adverse effects like SIDS in the case of infants, gastrointestinal problems, cardiac problems and some other life threatening effects. They are various types of milk based on some strategy, not all categories of milk do cause harm but based on genetic variation in their chain shows its cause action, ,why this change has occurred in milk among them and action of the dangerous metabolites is explained In conclusion, the role of β-casomorphin in physiological functions remains controversial and more research with improved diagnostic techniques is needed to unravel the mechanism and study physiological functions of β-casomorphin and variation of the cow breads in world.