Hi Below 2 yr age group, rotavirus is the most common cause of diarrhea. It presents with vomiting, frequent and watery stools and fever. whatever be the cause, take care that he does not get dehydrated. Give him lot of fluids like water, vegetable soups, rice water, dal water, curd etc. If he is not tolerating the routine formula, you may try soya milk. Avoid fruit juices. You may give medicines for vomiting (Domperidone). You may give him probiotics too. At any time if he gets lethargic, runs high temperature, skin and mouth are dry or urine frequency is very less, you must take him to your Pediatrician as these symptoms suggest dehydration. If you see blood in stools, do consult your pediatrician as it may suggest bacterial infection that should be treated with antibiotics. Try to stop his bottle at the earliest. Hope you find my answer helpful.