I've had multiple brain scans - ct, mra, mri. have dizzy / fogginess and pressure in head worsened by bending over. all caused by allergies?

Dizziness: The most important point is a history of what you mean by 'dizzy' , time of day and other factors including medications, over the counter supplements, and allergies. A careful examination with blood pressures in both arms as well as changes in blood pressure and pulse from lying to sitting to standing as part of a basic physical examination would be good. Consult an internist or neurologist.