How Can Hives On The Body Be Treated?

My grandson (4 years old) has broken out with what looks to be hives, because it is red and raised areas on his back, chest, waist, top of legs, shoulders and face. It has happen yesterday and lasted about 45 minutes and disapeared altogether. Then today he broke out again with more hives than before. He didn t have them on his face yesterday, but today he also had hives on his face. We checked with parents and they said he had nothing different than before and the same with being with me. Nothing different. He is getting over a mild cold and had a mild case of pink eye last week. He also had a tick in him about 3-4 weeks ago. A deer tick which his mom tried to pull out, but the head was stuck in his skin at his neck and the doctor told them to just wait and it will come out on it s own. And... it did, but....I am always suspicious of ticks and the good old lyme disease. Not sure what it could be and what is happening to him. He seemed a little irritable today his Mom said. Thank you so much for your advice! Very much appreciated from a concerned grandparent!