Cabin humidity and dehydration
The humidity in aircraft cabins is low, usually less than 20% (humidity in the home is normally over 30%). Low humidity may cause skin dryness and discomfort to the eyes, mouth and nose but presents no risk to health. Use skin moisturizing lotion or a saline nasal spray to moisturize the nasal passages. Wearing eyeglasses rather than contact lenses can relieve or prevent discomfort to the eyes. The available evidence has not shown low humidity to cause internal dehydration and there is no need to drink more than usual. However, since caffeine and alcohol have a diuretic effect (causing more urine to be produced), it is wise to limit consumption of such beverages during long flights.