my dau broke hives around mouth, ears and stomach areas when we fed egg. kkh paeds tested and confirmed she has egg allergy. we were informed that the hives presented in those areas are ingested food allergy. if you are concerned and just to clear your doubts, can request allergy testing at kkh. we had a skin prick test. we were informed, if a baby is presented with a certain allergy, they may be allergic to other types of food or things as well. we were given anti histamines in case any hives broke out again. we were told to observe. we found out later baby also had hazelnut allergy. kkh taught us on what are the foods to watch out for and how to observe and the quantity to give baby new foods. the hazelnut allergy presented similar like your baby. only in arms, stomach and back. its a milder reaction than the egg allergy.