Can An Itching Thigh Rash With Facial And Back Hives Be Treated?

my 4yr old son gets a rash that come and goes on his inner right thigh he states its itchy .also now 2 times in past week he got the hives on his face and back ....I thought it was soap that I bought so I stopped but now I think it could be strawberries . he has had berries in past but today after he had them he got the hives again .