The two biggest factors that cause allergy sufferers to experience problems on planes is the change in cabin pressure, particularly during descent, and the low humidity of the cabin. The change in pressure often leads to swelling of the sinus openings, with subsequent sinus headaches, and closure of the eustachian tubes, with secondary ear pain or even bleeding into the middle ear (middle ear hemorrhage). The best method for preventing these symptoms is the use of an over-the-counter topical decongestant, such as oxymetazoline, 30 to 60 minutes before the plane begins its descent.
Taking your daily allergy medications before, during, and after the flight, according to your usual schedule, is also helpful. Low cabin humidity, which is normal during flights, leads to increased dryness of the nasal mucous membranes, which may further aggravate nasal, sinus, and eustachian tube swelling. To help counteract this problem, a saline nasal spray every 2 hours during the flight can help. In addition, increased oral intake of fluids may also be useful. Alcoholic beverages, which are known to increase urination, may reduce your state of hydration and are therefore best avoided on plane trips by individuals with nasal allergies or sinus problems.