Extreme allergies are your immune system over-reacting to foreign agents. It sees relatively harmless particles, assumes they're out to get you, and calls out all the troops.
(Correct me if I'm wrong)
Instead of a symptomatic fix, you should look into food and chemical intolerances. My guess is you'll find something.
Allergies are an overreaction to what should be harmless foreign agents. There are some dubious practitioners who claim that food 'intolerances' are related to allergies, but in this extensively researched area, there is little evidence to actually support this.
The most popular theory of allergies is that they are an over-reaction, because the immune system has had nothing else to fight. The immune reaction to allergies is a very specific method that was developed to fight parasites (watering eyes, runny nose, coughing, sneezing are all ways that the body could rid itself of parasites). However, because of the cleanliness of modern living, the immune system never gets the experience it needs to regulate its activity.
For treatment of mild allergies, I normally use a non-drowsy antihistamine - loratadine (clarityn), cetirizine (zirtek) and fexofenadine (telfast/allegra) are all much the same as each other. Fexofenadine is probably the most powerful, but is prescription only.
If sneezing or runny nose is a serious problem then a nasal spray with a mild steroid, is useful - but you do need to use it for about a week before it really starts to make a difference. These can usually be obtained OTC.
Similarly, antihistamine eye drops are useful if eye symptoms are the troublesome, but again, prescription only, I think.
If symptoms really are troublesome, then a discussion with your doctor to find an appropriate treatment plan and/or assessment at an allergy clinic would be a very good idea.