If it is not itchy, my son had a same situation. The doctor said it was a reaction due to body is fighting virus so hard. It will disappear in a couple days. But yes, it looks scary.
just suggestion : discuss these with you doctor or go to see doctor even if he is getting better.If there are red spots on feet or hand ,it possiblely scarlet fever,you baby need eat some antibiotics ,it's delicouse not difficult for baby