It's not, you need a prescription, but it works for me more than anything else. There is a generic form of it so it shouldn't be that expensive. If you need something OTC, I'd suggest taking a sudafed (if they don't make you drowsy), not the kind you can buy off the shelf but the one they keep at the pharmacy. I don't know if they're good to take daily/long term because I think they can raise your blood pressure.
Also, instead of taking benedryl, you could try zantac instead. It's known as a heartburn prevention drug but it's also an antihistamine like benedryl is, without the drowsy side effects. My doctor recommended it to me once when I was having an allergic reaction that benedryl wasn't kicking. It's over the counter and not that expensive.
You should probably talk to your doctor before you do anything though. Getting on allegra seriously changed my life but different things work for different people.