text: There are hundreds of different types of rashes, and even more possibly causes. It could be a symptom of something else, or it could be a disease all its own. Could be an allergy, could be a fungal or yeast infection, could be idiopathic (no known cause). Without a description of what the rash looks like, no one can tell you what it is. See a doctor.\n\nI assume you mean the drug cetirizine, which is the antihistamine commonly known as Zyrtec. Many people, myself included, use antihistamines daily on a long term basis, without any ill effect.