High blood pressure does not cause eye allergies, but it can affect the blood vessels in your eye, causing damage and vision problems. This condition is called retinopathy, and it can cause irreversible damage to the retina and even blindness if left untreated.
The higher the blood pressure and the longer it is left untreated, the more severe the damage will be. Control of high blood pressure can prevent further changes in the blood vessels of the eye.
Some medications for eye allergies can cause blood pressure to increase, and are contraindicated for people who have hypertension. Many decongestants in pill or liquid form are available over-the-counter. They can relieve nasal and sinus congestion caused by hay fever, but they may have unpleasant side-effects and may be dangerous if you already have high blood pressure or heart disease. Nasal decongestant sprays can also increase blood pressure and can cause dependency, as well. If you have a chronic disease, consult your doctor before taking any allergy medication.