My 5yr old is really allergic to dogs and cats but loves animals , is there a chance if i got him a hamster he would be allergic to that also ?

Possible: Some animal danders do cross react but see an allergist who can test to see if there is a hamster allergy specifically.

There is a chance: The best answer is to get him skin tested to know for sure. The other option is to visit a friend with a hamster or go to a pet store to see how he reacts before buying him one. If the hamster is not in his room then he is less likely to react to it but if he has an allergy then it would be best to not buy one.