Sometimes contact lenses cause me to have gpc. What is it and how can it be treated? Is it considered an allergy?

Eye Issue. It could be an allergy. But it could also be irritant conjunctivitis, vernal conjunctivitis, or something else. An ophthalmologist is best trained for eye treatment. Ni disrespect to optometrists' but i would seek help 1st from an ophthalmologist.
GPC. Reactipn to plastics or antigen attachung to plastic. Have your dictir switch you to daily disposable lenses. Proclear lenses ate treated so that deposits don't attach.