@Melonlity -- if you are the type that would rather avoid antihistamines, there is a natural way to deal with the conditions that could cause allergic reactions and the post-nasal drip that could follow.
A lot of companies sell a kit that will allow the owner to mix a saline solution and wash out their sinus passages with it. That process removes a lot of the pollen and other contaminants that could kick off an allergic reaction.
The process isn't too pleasant at first, but it is effective and users do tend to get used to it in a hurry. Besides, you don't have to deal with the grogginess that sometimes comes with antihistamines and, by extension, the post-nasal drip that could result from allergies.