G.B.
His body is still deciding if he's going to have allergies or not so allergy testing won't be too helpful even if you could find someone to do it at 3. Give him half a dose and see if that still works. I always go easy when treating the kids. I use less if at all possible.
Almost every allergy med dries the kids out and they start getting worse or starting other behaviors or illnesses as a result of being to dry.