I think my child is allergic to my puppy!

[RockysMum]

Hello everyone,
I beleive that my child is allegic to my new puppy,we have had him for 10 days and my child has been fine but this morning my child said that he had a sore back.When i looked he has a rash about the size of a 50p pence on this back and it deof looks like a allergy rash.Im so gutted aand so is everyone else as we desperately dont want to get rid of our puppy as we all love him so much already.
Is there anything that i can do to help my son and to treat the allergy so we dont have to get rid of the puppy?

Any advice would be great pls xx.