Which is a stronger drug Benedryl or Zyrtec? Please help!?

I am 20 and I am having really bad allergies that is causing me to wheeze (I'm asthmatic). I am looking for an antihistamine that will not only help with my allergires, but will last a long time and not wear off so quickly. Right now I am taking benedryl which is helping with my asthma, but when it waers off in like 4-6 hours I start wheezing. When I start having problems with allergies I start to wheeze. So I need something that will tackle my allergies and is strong enough to last the WHOLE day. Also does Zyrtec help with the treatment of hives?