Cindy, There are many over the counter products available these days for allergies, including the big 3: Claritin, Zyrtec and Allegra (and their generic equivalents). I'd ask the pharmacist if they are safe to take with Adderal XR, just to be sure, but I haven't heard that this is an issue.
You don't say how old your son is, but another possibility is to use a nasal rinse, such as a NetiPot. I talk about that and other alternative allergy treatments here.
Hope that helps,