Little red dots

So my LO was sick on Saturday so I assumed he was teething, had a fever and everything. So I gave him Tylenol, oral j, teething rings, the whole nine. Then Sunday I go to work and my husband tells me the baby has little red dots all over his body. We bring him to the ER and the doctor says he’s not teething but has a viral infection. Says it was clear up in days. But now today it got worst and spread to his face. Does anybody have any idea what they really are will they go away? My sister said it could be from allergies or from a vaccination shot he got two months ago. Any suggestions