###Human: On shifting from cow milk to formula milk my baby gets fever and vomiting. Why? ###Assistant: Hello,  Welcome to icliniq.com. Cow milk should not be given until 1 year of age usually, as it may cause calcium and iron deficiency. Any change of feeds in babies can cause some change in stool pattern. Which formula are you giving and how do you prepare it? Proper concentration is very important. Have you started weaning? And how many times the baby is feeding milk? If only two or three times then you can continue with cow milk but do not dilute it.