I took 2 clairton a day for 2 years and then had to switch to zyrtec (cetirizine) for 1.5 years i think its not working if i switch back to clairtin will it work?

See a doctor: If you are using zyrtec, (cetirizine) and still having symptoms then you need to see a doctor. 2 claritns may work.

Visit your allergist: It sounds like you are having significant allergy symptoms and it may be worth seeing a specialist about these symptoms. We have many medication and treatment options that may help relieve your symptoms.

Probably not: Zyrtec (cetirizine) is a more effective antihistamine than Claritin (loratadine) . Antihistamines do not become less effective with prolonged use so if your symptoms are worse while in zyrtec then the underlying condition has become more severe so the same dose of zyrtec is unable to control the symptoms. Call you doctor and consider consulting a specialist in allergy & immunology.