What are ways to reduce eye swelling as a result of seasonal allergies?

Oral antihistamines. Most oral antihistamines will help to reduce swelling around the eyes caused by allergies.
Cool compresses. A damp washcloth over your eyes a few times a day can be very effective in relieving the swelling due to allergic rhinitis. The nasal steroid sprays, (prescription) can also help the puffiness and dark circles. It is felt that these symptoms are due to nasal congestion and the associated congestion of the blood vessels around the eyes.