My daughter was allergic to formula milk from day one, although we weren't aware of her allergy until some time later when after so many weeks of projectile vomitting and me trying to convince the GP's there was something wrong with her (she was losing weight etc) I finally had the diagnosis of an allergy to formula and cows (we tried both) at about 6 months of age so we had to put her on prescribed soya formula. She couldn't tolerate anything with cows milk in it - whether it be butter, cheese, yoghurt, cakes, bread etc etc....she lived off Alpro soya yoghurts and soya was put in with any meals I cooked for her. Once she got to about 18mths old she suddenly started keeping cheese and yoghurt down (only because she was helping herself to her elder sister's food!) so we had her checked by the specialist that was dealing with her allergy and we were advised to gradually introduce cows milk into her diet. After a few weeks of weaning she was fine. If she ate anything with cows milk/normal formula she would be immediately sick, a rash would develop around her trunk and she would go very snotty. We found it was quite common with children to be allergic to cows milk - its usually either an allergy to the lactose or protein. The same applied to eggs with her - I smeared a tiny amount of raw egg on her face to see if she developed a rash, which she did - much kinder to check eggs out this way rather than feed it to them and then be ill.