Travel Health Service Air Travel
Enviromental health risks

Air Travel

The aircraft cabin environment can be rather hostile and many travellers complain of different discomforts. Those with pre-existing medical problems may be adversely affected. Travellers should therefore take precautions whenever necessary.

General health problems

Cough: Allergens, dry air, fumes and ozone in the cabin air may cause many passengers to cough more during the flight. Breathing through a handkerchief may help.

Dehydration: Cabin air conditioners remove most moisture from the cabin air by 3 hours into the flight, reducing humidity to an uncomfortable 10% to 20%. This dries out the mouth, throat, eyes and skin. Sucking on hard candies can relieve the dry feeling in the throat. Eye drops help those who must wear contact lens. Skin moisturizers will make skin feel more comfortable.

Nausea and vomiting: Low atmospheric pressure expands air in the gut by about 20% - 30%. Eating smaller portions before and during flights and avoiding carbonated beverages help minimize problems. Motion sickness may cause vomiting.

Headaches: Lots of factors, like tiredness, insufficient oxygen, odours, can increase the risk of migraine and other kinds of headaches. Headache remedies are most effective if taken as soon as pain begins. Breathing through a wet towel may help travellers avoid inhaling fumes.

Fainting: Lightheadedness is the commonest cause of in-flight medical problems. Hyperventilation is a common symptom. Fainting is generally a harmless condition and is self-limiting. Victims generally respond to reassurance and to lying down with their heads lower than the body. But in the flight, fainting may be difficult to distinguish from other conditions like heart attack. Whenever in doubt, oxygen should be given.

Motion sickness: Few people feel motion sickness on jetliners, but such illness is common on small aircraft. Symptoms can be minimized if one fasts for 3 hours before flight, eats three small meals in the 24 hours before flight, and takes mostly carbohydrates.

Earache: Ear pain is especially common in children. Commercial airlines pressurize air cabin to the equivalent of about 2000 metres altitude. During taking off, air within middle ear expands and moves out through the Eustachian tubes to the nose. This generally runs smoothly. Problems arise during descent when air needs to travel back to Eustachian tube to equalize the pressure. At this moment, the Eustachian tube acts like a soft rubber tube, making it difficult to suck air back into the tube. This is what causes pain in the ears of young children. Nursing children with a bottle during descent helps the pain, as sucking and swallowing motions tend to open the Eustachian tube.

Leg swelling: Prolonged sitting in cramped quarters causes pooling of blood in deep veins of lower limbs, resulting in leg swelling. In addition, blood clots may form inside the veins. If the clots travel to the lung, they can cause a serious lung problem. The table below shows the risks factors of and ways to minimize blood pooling in the legs.


Risk factors of blood pooling:

chronic disease and malignancies

recent injury to lower limb

recent surgery, especially lower limbs & Abdomen

varicose veins, previous clots in blood vessels

long flights




oral contraceptives

Ways to minimise blood pooling:
loose underwear

frequently flexing and extending feet

walking about the cabin

not sitting with legs crossed

keeping the back of the knee away from the edge of the seat

avoiding sleeping pills

leaving the space under the seat in front clear for legs stretching

drinking plenty of fluids

wearing support hose

Concerns for people with medical problems

Anaemia: In healthy people, the blood oxygen level in usual flying altitudes of jetliners is easily tolerable. In anaemia, there are fewer red blood cells to carry oxygen to other parts of the body. People with a haemoglobin concentration of less than 10g/dL should check with their physicians before travelling by air.

Asthma: It is not clear if air travel is a risk factor for asthmatic attacks. However, most patients with asthma can handle their attacks in flight well with their standard medications. Emergency oxygen is available on aircraft but rarely necessary.

Heart and lung diseases: Generally, patients who can walk briskly about 90 metres or climb a flight of stairs without pain or shortness of breath should have no difficulty flying on commercial airliners. Patients with severe heart diseases should consult a cardiologist before flight as they may override those usual recommendations to delay air travel (e.g. 4 to 6 weeks after a heart attack), if indicated by some testing of heart function.

Diabetes: Diabetic patients should bring their own food and be familiar with ways of adjusting insulin dosing for crossing time zones.

Seizure: The risk of seizure increases in air travel because of oxygen insufficiency, meal irregularity, sleep deprivation and jet lag. Seizure-prone persons should travel with a companion or notify flight attendants about the remote chance of a seizure occurring.

Orthopaedic conditions: Travellers with preflight injuries, like ski injuries requiring leg casts, should obtain seats with sufficient legroom to allow elevation and/or movement of the limb to prevent pooling of blood. Some orthopaedists advise delaying air travel for 48 hours after a large cast is applied.

Dental conditions: Dental problems should be corrected several weeks before flight. Both tooth decay and dental procedure may cause small air pockets within the teeth. The air expands as atmospheric pressure decreases, resulting in pain.

Nasal congestion: Travelling by airplane when having swollen mucous membranes can cause pain in the ears during ascent and descent or, in rare cases, may even result in permanent damage. Jaw movement (e.g. swallowing, gum chewing) and Valsalva manoeuver (holding the nose closed and blowing into the nose to increase pressure in the nose) can alleviate the pain. Those who have severe chronic sinus diseases may benefit from decongestants, antibiotics and/or steroids during the week before flight.