Allergic eye symptoms can be triggered by the nose

The itchy, watery eyes that plague people suffering from allergies could be related to a reflex response triggered by the nose. Previous research has shown that when an allergen is introduced into a nostril, the other nostril responds, characterizing a phenomenon known as nasonasal reflex. Since the eyes and nasal cavity share a nerve supply, it's possible that ocular hay fever symptoms aren't only related to direct exposure to the allergy-producing substance, but could also be a result of a reflex response. To assess how the nose triggers allergic eye symptoms, researchers at the University of Chicago studied the reactions of 20 people, who were allergic to grass or ragweed, under experimental conditions. Each of these subjects underwent a test with an extract of grass or ragweed placed in the nose. In the next experiment, the researchers first sprayed a placebo or antihistamine into the nose, and then challenged them again with the amount of allergen that had produced a response in the previous experiment. The subjects then switched from placebo to antihistamine and vice versa, and were tested again. The results showed that the eye symptoms associated with allergic rhinitis probably arise, in part, from a naso-ocular reflex. It was found that when they had been given antihistamine before allergen exposure, symptoms were reduced in both nostrils, and eye symptoms also were reduced. To add to this, the fact that corticosteroids administered via the nose can also reduce eye symptoms provides additional evidence that eye symptoms are reflex-related. They conclude that allergic symptoms in the eyes may be related to allergy in the nasal cavity.