<s>[INST] my 2 month old is transitioning from breast milk to formula.  I was feeding him 1 bottle of similac advance for about 5 or 6 days and the last 2 days after feeding him the bottle he broke out into a bad red rash with white bumps all over his back, arms, face, neck and legs.  What could it be? [/INST] Hello. Thank you for asking at Chat Doctor. I went through your sons history and would like to make following suggestions for him:1. He may be reacting to any of the contents of the baby food. Personally I would suggest you to withhold the baby food for a few weeks and then reintroduce under your pediatricians' guidance. If apart from rash, your son has any other symptom like fever, cold limbs, vomiting, diarrhea, not feeding well, lethargy, etc., it may indicate an infection, and please consult your pediatrician immediately.2. For prevention of allergies & infections, only breastfeeding up to 6 months of age and introduction of other foods only after 6 months is the best strategy. So unless necessary, I would not suggest you to introduce any food/formula before 6 months of age. Hope above suggestions will be helpful to you. Wish your son the best of the health. Thank you & Regards. </s>