What Should I Tell My Healthcare Provider?You should talk with your healthcare provider prior to taking cetirizine if you have:
- Kidney disease, such as kidney failure (renal failure)
- Liver disease, including liver failure, cirrhosis, or hepatitis
- Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you are:
- Pregnant or thinking of becoming pregnant (see Zyrtec and Pregnancy)
- Breastfeeding (see Zyrtec and Breastfeeding).
Make sure to tell your healthcare provider about all medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.
(Click Precautions and Warnings With Cetirizine to learn more, including information on who should not take the drug.)
How Does It Work?Allergies occur when the body's immune system reacts to normally harmless substances that do not bother most people. This reaction is partly caused by the release of histamine from certain cells in the body. Cetirizine is an antihistamine, which means it blocks histamine from binding to histamine receptors and causing allergy symptoms. Since histamine is responsible for many of the symptoms of allergies, blocking it can be helpful. It is important to note that antihistamines (including cetirizine) do not help treat nasal congestion caused by allergies, since this symptom is not due to histamine.
Histamine is also responsible for the formation of hives (whether they are caused by allergies or not). Cetirizine works to alleviate the itching due to hives by blocking histamine.