I am uncertain what causes the hives I get, it may be from the plants in my garden, cactus etc, but they have been severe this year I thought once fall came it would ease off but it is worse. So which OTC would help me , is Zyrtec worth trying I have tried claritin doesnt do anything ,and do these kick in straight away or take a few days to work,yhe burning and itching I get round my neck ,tops of arms is really painful . the anti histime hydroizone I had from the Doctor last year made it worse. Thank you