4mth baby - rash on face?

My 4mth old has a rash on his face, it started out as a few red dots which i assumed were just pimples but it has spread into a rash which is in his chin, above his top lip and under nose and he also has red bumps on his eyelids. It doesnt seem to irritate him. The texture of the rash has gone scaly. I've been told by a pharmacist that it could be teething rash from drool but i'm not sure as he has it on his eyelids. Any ideas what it could be? I'm going to take him to the doctor today anyhow just to have it checked out.