Neocate has made my 5 months old a whole new baby. I really don't see any side effects, but his bm's smells like rotten eggs and are dark green...I personally have no problem with this as before he was on the neocate I was changing 10-15 diapers a day with bloody diarreha. Also the cost can be quite pricey, but I would pay anything for a healthy baby again. I love the stuff!!!