Hello, hives are not normally caused by zyrtec. Actually zyrtec treats hives! Hives usually recur particularly after the blood levels of the antihistamine start to drop. Sometimes higher than normal doses are required and/or the addition of corticosteroids. The cause of hives should be addressed too. It could be a new drug, new scent, new food, anything... You ll need to talk in detail with your doctor to identify (if possible) the offending factor. Regarding your abdominal complaints, this kind of symptom is not typical. Abdominal pain cannot be approached diagnostically without clinical examination data. They are very very important. Persistent abdominal pain (lasting for more than 6 hours) requires urgent investigation. Please contact me again, if you d like more information or clarifications. Kind Regards!