Hi Mary,   No worries... Zyrtec is one of the second-generation allergy medicines, which also include Allegra (Fexofenadine) and Claritin, all of which are considered extremely safe to take and have very few side effects. They are designed for long-term use.   If your child is on other medicines, it is important to discuss this with your pharmacist or doctor to be sure Zyrtec won't interact in a negative way with those medicines (most asthma medicines are safe). The kinds of drugs most likely to interact with Zyrtec are: prescription pain relievers, antidepressants, muscle relaxants, sleeping pills, and high doses of Theophylline.   Also, if your child has kidney or liver disease, any medicine can be potentially dangerous and the kidneys and liver are responsible for breaking down the drug and getting rid of waste products.   Many people, both children as young as 2 years and adults, take Zyrtec safely for many years. But be sure to voice any concerns, including unexpected effects, to your child's doctor.   To your health, Kathi