Zyrtec® (cetirizine hydrochloride). One uncommon side effect, occurring in less than 2 percent of people taking Zyrtec, is a decreased sex drive (libido). Given how rarely a decrease in libido occurs in people taking Zyrtec, it is not possible to say whether it is caused by the medicine, other factors, or a combination of both. Furthermore, it is impossible for your healthcare provider to know beforehand if Zyrtec will have an effect on your libido.
If you develop any sexual side effects (including a decreased libido) while taking Zyrtec, talk with your healthcare provider. He or she may be able to recommend treatment options. Depending on how severe your symptoms are, your healthcare provider may also recommend that you adjust your Zyrtec dosage or try another medicine.