Random Hives, no reason, happening for years

[Purple1144]

For pretty much the past 6 or 7 years, I constantly break out in hives whenever I touch anything. It could be that I sit on a chair and get hives on my thighs or open the fridge and get hives on my hands. I've gone to a dermatolagist several times, but even after a scratch test and everything, we've found no reasons for my random breakouts. I'm currently on Allegra and have been for years. I've tried claritin, zyrtec, etc. I need to know what ttis is and how to stop it! Any help is great! Thanks!