How To Treat Flea Bites?

Hello yes my name is Josie, I'm trying some help my grandson with fea bite, I've taken him to the ER, doctor and nothing seem to work. Plz help me. I'm sorry I don't have the money to get the answer. I'm disable and doesn't work and on fit income, so I'm going to have till I can get the money so I can get the answer.thank you