Hi..this could be an allergic reaction. But another important point you need to recollect is that if you had fed the baby any cow s milk product recently. This also could present like this. Even cow s milk products in your diet - the cow s milk protein will get secreted in breast milk and can affect the infant like this. My suggestions for you - 1. Mother should go off cow s milk protein completely. This means that you should avoid consumption of anything and everything related to cow s milk - like - milk/ curds/ ghee/ butter milk/ chocolates/ biscuits/ ice creams etc. Even while buying commercial food products, you need to see the ingredients and if they contain milk - do not consume them. 2. Feed you baby only exclusive breast feeds till 6 months of age and then start rice based feeds. 3. If this is followed scrupulously - the baby will stop having diarrhoea in another 3-4 days and then start gaining weight too. 4. If you feel your feeds alone are inadequate for the baby, then Zerolac is the only option till 6 months age. I request you to keep me posted about the recovery of the baby and follow of the case. Regards – Dr. Sumanth