Red itchy bumps behind ears

AB

My 13 month old son keeps getting these huge red raised itchy bumps behind his ears. At first he got one behind his left ear and we thought maybe it was a mosquito bite. We put cream on it and it went away after couple of days. Today he has those bumps again behind both of his ears so now we don’t know if it’s mosquito/bug bite. Anyone have any idea what might be causing these bumps?