First off: why seek medical advice on a headphone forum? Might as well ask your mother.
Nevertheless:
For instant relief, use Benadryl. Carry a couple in your purse/wallet/whatever. I carry some of the Listerine-style quick dissolve strips. Benadryl makes some people very drowsy, so be careful if driving, etc.
For day-long relief over a season, use Claritin or Zyrtec. I prefer Zyrtec myself. Note that drinking alcohol or eating fatty foods can affect the metabolism of the drug in the liver, and attenuate the effectiveness of the allergy drugs.
For persistent problems with inflammation, go to your doctor and get tested for allergies. They can prescribe anti-inflammatory steroids like those mentioned above in this thread. Taking steroids too long can have unwanted effects, obviously.
There are currently only 2 long term solutions to airborne allergies: 1) remove your exposure to the allergen by relocating, setting up HEPA filters, wearing an appropriate filter mask, etc; 2) get allergy shots, which work well for some.
Nasal sprays can be addictive (Afrin, etc). Many of these are over-the-counter treatments in the USA, but you really should be consulting a physician if you use them for more than a day or two.
*This is advice to inform yourself and seek a personal medical opinion from your local physician, and is not to be construed as medical advice itself.