I take otc allergy meds everyday. i heard it can be helpful to switch otc allergy meds every 3-4 months. is this true? zyrtec, claritin, (loratadine) allegra?

Ask an allergist: I think most clinicians agree that if a drug proves efficacious, meaning it works well for you personally, you continue to use that drug for as long as it works well. If you find that none of the OTC allergy drugs work well for you, then, with the help of your primary doctor, attempt to find the one that works best and stick with it.

Similar medications: The medications you mentioned have the same mechanism of action. Everyone's body may have a different response to medications. Some studies have indicated that tolerance to antihistamines does not occur however switching to find which works best for you is reasonable. The best medication = the one with lowest side effects and works! Consider saline and nasal steroid spray or allergy testing.