My 4 year old son got his vaccinations Thursday. He has never had a reaction before. Last night I found that at the site of one injection , he has a large red welt. About 2 in diameter, hot, swollen (but soft to touch). It does not appear to hurt him, and now seems to be itching a little. The Vaccinations were: Diphtheria/Tetanus/ Pertussis , Polio , and MMR . I gave him children s ibuprophen last night and just a while ago. I tried benadryl this morning but that did not seem to do anything. Do I need to bring him in to the doctor?