Hi....it could be cow s milk protein allergy. I went through the history points you have provided - I was expecting that there should have been a history of cow s milk and formula feed (this too contains cow s milk protein) given to the baby. I feel that your baby is having cow s milk protein allergy. Unusually babies grow out of this sort of allergy by 1 year of age. 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 up of the case. Regards – Dr. Sumanth