I'm looking for a natural antihistamine for seasonal allergies rather than using zyrtec (cetirizine)?

Natural treatments : Natural treatments are medications too. Usually not as well studied or characterized for benefit and safety as those approved by the fda. I don't know of any natural antihistamines per se but butterbur has been reported to have benefits. A very safe alternative to allergy medicine is buffered saline washes. These can be purchased or home made but certain hygienic guidelines should be followed.

Why Natural: As was stated by one of the other doctors, natural treatments are medicines too but less well studied and standardized with more potentially unknown side effects. They work at the same places and receptors in the body and because potency is not standardized they may have unforeseen consequences. Also, many natural medicines may be related to things you are allergic to.