Hi there, Although not the first choice I for my patients, Phenergan can be used to treat allergies and also is used for nausea. It is an antihistamine, similar to benadryl. A medication with less side effects that I really like using is Flonase, which you can get over the counter now without a prescription. I personally suffered from bad post-nasal drip, and Flonase worked great with minimal side effects. On top of that, I was able to stop it after a week and all my symptoms continued to be relieved without continued use. Hope this is helpful. Feel free to contact me with any further questions!