The unique environment of an airplane cabin presents a combination of physiological challenges and increased exposure risks that can affect a traveler’s health. While modern air travel is remarkably safe, the shift to a pressurized, low-humidity, and confined space can lead to temporary physical discomfort or susceptibility to illness. Understanding these distinct conditions is the first step in mitigating their effects. Health concerns fall into two main categories: the body’s non-infectious response to the altered atmosphere and the potential for germ transmission in a dense, enclosed space.
How Pressure and Altitude Affect the Body
Commercial aircraft are pressurized to maintain a cabin altitude equivalent to about 6,000 to 8,000 feet above sea level, which is a significant change from the air at ground level. This reduced barometric pressure causes gases within the body’s closed cavities to expand, leading to the common sensation of pressure or pain known as barotrauma. The middle ear is particularly susceptible to this effect, as its pressure must be actively equalized with the cabin pressure through the Eustachian tubes.
The Eustachian tube, a narrow passage connecting the middle ear to the back of the nose and throat, is normally closed. Swallowing or yawning causes muscles to open it momentarily. During ascent, cabin pressure drops, creating positive pressure in the middle ear that naturally vents. Descent is more challenging because increasing cabin pressure creates negative pressure in the middle ear, which can seal the tube closed and cause pain or a blocked feeling if not equalized.
The simulated altitude also results in a mild reduction of oxygen in the blood, a state called mild hypobaric hypoxia. For healthy individuals, this results in a small drop in oxygen saturation. Symptoms of this mild hypoxia can manifest as fatigue or a light headache. However, for those with pre-existing cardiopulmonary conditions, this reduced oxygen level can be more taxing on the body.
Another factor is the extremely low humidity in the cabin, often between 10% and 20%. This dry air accelerates moisture loss, quickly leading to dehydration, dry eyes, a scratchy throat, and dry mucous membranes. This dehydration, combined with the prolonged immobility required by long-haul flights, contributes to the risk of deep vein thrombosis (DVT). DVT is the formation of a blood clot, often in the legs, a risk elevated by blood flow stagnation and mild hypoxia.
Understanding Germ Transmission in the Cabin
The risk of contracting an infectious illness while flying is often misunderstood, especially concerning the quality of the cabin air. The air in modern aircraft is refreshed at a rate of 20 to 30 times per hour, which is substantially higher than the air exchange rate in most office buildings. This circulation system uses High-Efficiency Particulate Air (HEPA) filters, which are similar to those found in hospital operating rooms.
HEPA filters are highly effective, capturing 99.9% or more of airborne microbes, including viruses and bacteria. The cabin air system operates by mixing approximately 50% fresh air drawn from outside the aircraft with 50% HEPA-filtered recirculated air. Furthermore, the airflow pattern is generally top-to-bottom rather than front-to-back, which limits the longitudinal spread of airborne particles throughout the cabin.
The primary mechanism for germ transmission is close physical proximity to an infected passenger, not the recirculated air. Respiratory illnesses are mainly spread through droplets expelled by coughing or sneezing, or through contact with contaminated surfaces. Studies suggest that the highest risk of infection is for passengers seated within two rows laterally and two seats across from a contagious individual.
The movement of passengers and crew contributes to the spread of germs to surfaces, known as fomites. High-touch surfaces like tray tables, seatbelt buckles, and lavatory door handles can harbor viruses and bacteria for a period of time. The true transmission risk is a combination of close-range droplet exposure and contact with surfaces.
Simple Steps to Stay Healthy While Traveling
Managing the effects of pressure changes requires active measures during ascent and descent. To help the Eustachian tubes equalize pressure, passengers should frequently swallow, chew gum, or gently yawn. If the ears feel blocked, the Valsalva maneuver—pinching the nose shut and gently blowing air into the closed nostrils—can force the tubes open to relieve discomfort.
Counteracting the low humidity requires prioritizing hydration throughout the journey. Drinking water consistently and avoiding excessive consumption of dehydrating substances like alcohol or caffeine helps maintain moist mucous membranes. Packing a saline nasal spray can also help keep the nasal passages from drying out, providing a better barrier against inhaled irritants.
To reduce the risk of DVT on flights longer than four hours, travelers should avoid prolonged immobility. Simple exercises can be performed while seated to encourage blood circulation in the lower legs:
- Perform ankle circles and heel-toe raises.
- Stand up to walk the aisle every hour or two.
- Wear compression socks to assist blood flow and prevent swelling.
Reducing the risk of germ exposure relies on personal hygiene and awareness of high-contact surfaces:
- Wipe down surfaces such as the tray table, armrests, and seatbelt buckle with a disinfecting wipe.
- Wash hands frequently with soap and water.
- Use an alcohol-based hand sanitizer containing at least 60% alcohol.
- Avoid touching the eyes, nose, and mouth to minimize pathogen transfer.