Allergen avoidance. The best one off course is to avoid the allergen completely if you can. Many times, you can't either because you don't know the allergen or you can't really avoid the allergen. So, in that case, you can try otc medication like anti histamin (benadryl) or other medication like claritin, (loratadine) zyrtec, allergra etc. Try one- see which one works better for you. Discuss further with your doctor.
Several. Over the counter you have allegra, zyrtec and Claritin and saline nasal spray. Prescription medications are numerous and the ltimate in long term relief is allergen desensitization. See an allergist to discus. Your options.