While flying is one of the safest modes of transportation per kilometer travelled, it can put pressure on the mind and body.

This article contains general advice, followed at the reader's own risk. None of it should be taken as medical advice. If you have health issues that might be complicated by flying, consult your doctor.

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Common issues

The following issues and remedies are for those travelers with extra concerns about some conditions. Most people do just fine with a bottle of water, and perhaps a neck pillow and an eye mask for sleeping. For very long flights, extra measures may be useful, as noted below.

• Your nasal passages can dry out during multi-hour flights. This will make you uncomfortable and slightly more susceptible to airborne infections. Drink plenty of liquids (without alcohol or caffeine), perhaps use a moisturizing nasal spray (e.g., saline solution rather than topical anti-histamine). Consider using a face mask on long flights to conserve lung and sinus moisture. (Masks may otherwise offer only marginal protection against airborne disease; sterile cloth masks may work slightly better than formed, single-use paper ones.) Cabin air is very dry, firstly because ambient air at -40 degrees contains basically no humidity and secondly because metal planes cannot handle humidity all that well. This can of course also cause problems, but the effect most passengers note immediately is a changed taste perception. The newest generation planes made out of composite materials, specifically the Airbus A350 (recognizable by its "eye black" around the cockpit windows) and the Boeing 787 "Dreamliner" have somewhat more humid cabin air, improving passenger comfort.
• Bring some food with you, even if you don't have diabetes, don't have food allergies, and don't tend to get miserable when hungry, unlike about 99% of us. It could be as simple and portable as a granola bar (aka flapjack or oat bar). The point is to have something just in case your plane is stuck on the tarmac for hours, while tempers rise and blood sugars drop. See camping food.
• Cabin temperature can vary, and for window seats, the wall can be cool while airborne. Consider taking a coat, jacket or newspaper on board. Wear warm socks, and if in a window seat, put something between you and the wall. Even a few layers of newspaper help considerably. On the other hand, if you get stuck on the ground on a hot day, you may quickly find yourself uncomfortably hot. Consider dressing in layers, so that you can adapt to the temperature that you encounter.
• Contact lenses. On multi-hour flights, you should use re-wetting drops frequently, or consider wearing prescription glasses instead, especially if you hope to sleep during the flight. The very low cabin humidity can cause dry contact lens complications for your eyes. (As for any long trip, take spare contact lenses and prescription glasses.)
• Sanitizing wipes can be essential on board and in airports to clean handles on overhead storage bins, hands, tray tables, arm rests, and key bathroom surfaces that have heavy use and unknown or (perhaps) neglected cleaning. Choose pre-wetted packets rather than bottled liquid for security-check convenience. Avoid those only for hands (often leave a residue of glycerine on hard surfaces); and (if possible) opt for those that contain sanitizing ingredients beyond alcohol for effectiveness.
• If pregnant, consult your doctor for your particular circumstances. Generally, if you're less than 28 weeks with a singleton or twins, and have no complications or history of premature labor, you may be able to travel without medical clearance, but check with the airline. Between 28 and 36 weeks, it's generally safe to fly, but you may be required to have a letter from your healthcare provider, especially for longer flights and international flights.

Less common issues

• If you need oxygen en-route, check with the airline to see if the type you need is feasible; if so, have your doctor (through your travel agent or airline) arrange it or issue a "prescription" for it well in-advance. This is most commonly prescribed for people who are unable to climb one flight of stairs or walk 50 meters without oxygen. If you normally carry an O₂ source, ensure it can be carried on board and used there. Some airlines – notably Ryanair – don't allow you to bring your own oxygen on board and charge for the use of theirs. Unfortunately they're within their rights to do so. If your need for oxygen is due to COPD (emphysema) or other conditions that cause large amounts of air to be trapped in the lungs, then flying can be dangerous. If you need oxygen because you feel breathless even while sitting quietly, then your doctor may advise against air travel entirely.
• If you have asthma or allergies, bring your asthma inhaler(s) and your allergy medications on board with you. Bring these even if you don't think you'll need them. Even if you carefully checked with the airline to make sure that you had booked a no-smoking flight on a peanut-free airline, your seatmate could still turn out to be a cat-hoarding peanut salesman who was chain smoking cigarettes until just before the cabin doors were locked.
• If you are prone to motion sickness, consider taking appropriate medication. Vomiting is rare, but nausea is still unpleasant. Some, such as the scopolamine patch, need to be taken in advance of the flight. Also, consider booking the largest airplanes possible on your route, as the big behemoths are much less susceptible to turbulence and much less likely to trigger motion sickness than the bouncy little turbo-props.
• If anyone in your party has a disability in other ways (e.g., mobility, vision), you'll want the airline to know in advance, preferably as you book your flight. With few days' notice, they can make appropriate seat assignments, arrange assistance in the terminal, and notify the cabin crew of your needs. Beware: not all airlines are equally accommodating. In Europe, the task of bringing handicapped passengers on board is typically taken care of by airport employees, while in North America the airline is usually in charge. Make sure to contact the appropriate entity ahead of your flight.
• If ill (especially with anything that might be contagious), you really shouldn't fly. In the close quarters of a plane, perhaps for hours, with 200 or more people going eventually to countless places, you could start or spread misery, even an epidemic. You should defer travel until you have recovered. If an airline or airport personnel notice symptoms, you may be denied boarding. Good trip insurance can help with the expense of suddenly delayed travel.
• If you've had surgery or a plaster cast applied within the last week or so, you'd best avoid flying. Low cabin pressure can cause extremely uncomfortable swelling. Consult your doctor. A fresh cast will usually lead to you being denied boarding. Surgery on "hollow" body parts (like bowels or eyes) requires a longer wait (often 10+ days) than surgery on "solid" body parts (like arms) or uncomplicated heart attacks (can be as short as 3 days for low-risk people). The lower air pressure in the air causes any internal air to expand significantly inside the body, which can cause not just pain but sometimes permanent tissue damage.
• Fifty countries worldwide, including China, South Africa, Argentina, Australia and New Zealand require that insecticides (usually residual types) be used on planes. If the airline (e.g., Hawaiian Airlines) does not use residual insecticide, the plane may be sprayed in-flight before arrival in those countries. If you are sensitive to such chemicals, ask in advance what is used, so your doctor can determine if it will affect you.
• The low humidity of airline cabins can cause dehydration to your skin, hair and lips, especially if you are flying multiple times or the flights are long. Among some people, their sebaceous glands respond to the low humidity by overcompensating and producing more oil than necessary, resulting in oily skin and potential acne breakouts. To mitigate the effects of low humidity, stay well hydrated before and during your flight and keep your electrolyte levels replenished. You may also consider taking a small bottle of moisturizer or lotion with you on the plane within the 100ml liquid limit. Dry shampoo and conditioner powders are available which can help your hair retain the right amount of moisture. Lip balm may be used pre-emptively to avoid getting chapped lips.
• You are also exposed to higher levels of UV radiation than on the ground, making frequent flyers more prone to skin damage and melanoma. If you're flying during the daytime, avoid sitting close to the windows and consider applying sunscreen to the parts of your body that will be exposed. See sunburn and sun protection for further tips on protecting yourself from the sun.

Pressure changes

Air pressure is much lower at high altitude, and while a commercial aircraft cabin holds much of the pressure, in-flight cabin pressure is still much lower than on the ground, often equivalent to 8,000 feet/2500 meters above sea level. The Airbus A380 and A350 as well as the Boeing 787 "Dreamliner" have higher cabin pressure, equivalent to lower altitude (about 6,000ft/roughly 1,800 meters), providing a bit more passenger comfort. Low cabin pressure can generate great discomfort if ears or sinuses are clogged, e.g., by allergies or a cold. If congested, and if your doctor has no concern about complications, consider taking a decongestant (anti-histamine optional) an hour or so before departure. An extended-release form may be preferable for a long flight. If you hope to sleep, note that such potions make some people restless. See altitude sickness for prolonged low pressure.

As any flight descends, most people have some trouble with pressure in their eardrums. That's why babies/infants then often cry loudly, having been quiet during takeoff and throughout the rest of the flight. Pinching your nose, closing your lips and trying to exhale (perhaps several times until landing) can relieve the pressure.

To prevent the discomfort in your eardrums, try yawning or moving your jaw (chewing gum or eating something) during takeoff and descent. For infants, let them nurse to relieve the pressure, but don't wake babies up for this, as sleeping babies often manage this pressure transition without difficulty – and if they don't, then they can start nursing when they wake up naturally. Give older children something to chew, like gum. Another remedy is a product called "EarPlanes," which are disposable earplugs available for $5–10 at drugstores. The plugs are specially designed to regulate the pressure in your ears and can make flying much easier for people who suffer ear pain when flying.

Restrictions and advice for some of these conditions can vary by airline, flight distances/times, total times to your destination(s), and availability of quality care at each stop and destination.

This change in air pressure can result in difficulties for people with some specific medical situations. Expansion of air inside the body means that colostomy users will need to change bags more frequently. Medical devices, such as catheter cuffs, that are held in place through air pressure may need to use an alternate system, such as filling the device with water.

The lower air pressure also means that it's a little harder for the body to get enough oxygen. For most people, oxygen levels only drop by about 4%, but people with severe or unstable heart disease, lung disease, or anemia risk low oxygen levels (hypoxia) while flying, especially on longer flights. The airline may require a "fitness to fly" certificate from your doctor, and your doctor may require either normal supplemental oxygen or an advanced oxygen system, or may prohibit you from flying at all, especially if there is a risk that the added strain could cause that unpredictable angina to turn into a heart attack mid-flight.

The air pressure changes are dangerous for people who have recently been scuba diving. On a diving holiday, it is advisable to plan on doing something else – perhaps shopping or relaxing in a beach-side bar – during the last day or two. See Scuba diving#Preventing dive-related illness for discussion.

If you might be prone to breathing complications, avoid taking a flight with a destination much higher than your departure point; see Altitude sickness for details.

Deep vein thrombosis

	Note: The following discussion should not be taken as medical advice. Consult a doctor if you think you might have or be at risk for DVT during planned travel.

Passengers on long flights may be prone to deep vein thrombosis (DVT), which is essentially blood clots forming in the veins, most often in the legs. It actually affects anyone who remains seated for long periods, e.g., train or car passengers. The elderly tend to have greater risk than the young. You can take precautions to avoid it:

• Stretch and/or walk at least every 2 hours or so. Even a trip to the washroom and back is better than nothing.
• Do in-seat exercises, e.g., flexing legs and torso, rotating/flexing feet.
• When booking the flight, ask for an aisle seat. This will let you more easily get up and move around during the flight.
• Stay hydrated by drinking water, or other non-alcoholic, caffeine-free beverages.
• Consult your doctor to see if certain preventative measures are needed for you. They may include compression hose (ask about the right kinds and compression rates) or perhaps taking a blood-thinner (e.g., low-dose aspirin) shortly before your flight.

Be aware of the early symptoms (e.g., pain or swelling in a leg) which you may notice during flight or later. If suspected, seek medical treatment promptly. If neglected, the condition can become serious, even fatal.

See a more comprehensive article at w:Deep vein thrombosis.

Nicotine

See also: Tobacco

As practically all commercial flights are non-smoking, and airports except designated areas, habitual tobacco consumers might face withdrawal symptoms during a long flight. Smokeless tobacco or nicotine gum might be used as a substitute.

Jet lag

See also: Jet lag

While jet lag is not caused by flying itself, flying is the only way to move several time zones away too quickly for your internal clock to adapt. Symptoms can be aggravated by the stress and immobility that come from flying.

Medications

See also: Medications, Flight baggage

IATA guidelines apply the 3-1-1 limits (in metric equivalents) to all international flights. They impose 100ml (3.4oz) limits on all liquids, gels and pastes in cabin baggage, including aerosols, toothpaste, deodorant/antiperspirant sticks, and drinks including water. All containers for those liquids must fit in a single clear bag/pouch smaller than 20cm x 20cm or 1 quart. Each container inside must meet the 100ml/3.4oz limit. Some exceptions are possible, e.g., for medical necessities or baby care items.

Have documentation that all medications belong to you, e.g., labeled bottles, copy of the doctor's prescription. For some countries, you made need even more documentation. Take no more meds than will be needed on your trip, plus a few extra of each type for possible multi-day delays. Make sure that no substance is illegal in any transit country. For some countries, you'll need the country's written permission to carry the meds anywhere within its borders. Consult your homeland's "State Department" web site, e.g., .

• Some countries (e.g., Japan) may have unexpected restrictions on entering with basic medications, even at-home over-the-counter items, e.g., anti-histamines. They will be confiscated if discovered, and you could be charged with a crime.
• The consequences in a few countries for some medications can be severe, e.g., immediate confiscation, fine, arrest, possible prison.

As possible, place all medications and the transparent bag of 3-1-1 liquids where they can be easily seen at security check. If you need more capacity, place all Rx liquids and injectables separately in as few transparent bags as possible. Ensure all medications are kept in original containers/bottles clearly labeled by the issuing pharmacist. For international travel, wait to sort medications into daily or weekly dose containers at your destination if so desired. If presorted before travel, customs officials seeing this will have no proof of the contents and may declare all as contraband. Place all other liquids not meeting the 3-1-1 Rule in your checked luggage. You may be required to demonstrate the harmlessness of any liquid you're carrying on request by security officials.

Hygiene and infections

Germs can spread on flights like anywhere else. The distance travelled creates risks of transmitting an infection between countries. Fortunately, ventilation systems on planes use much more fresh air from outside and less recirculated air than the systems in most buildings, and most airplane ventilation systems filter out small particles.

Wearing a face mask on a plane

To reduce your risk of catching something from another passenger, practice usual good hygiene: wash your hands frequently, or use alcohol-based hand sanitizer if it's not convenient to leave your seat, and avoid touching your face.

Researchers have found that passengers in window seats have less risk of contact with sick people. If you're concerned about infectious diseases, try to book a window seat, and avoid moving around the cabin during the flight.

Before sitting down, you can use disinfectant wipes to wipe down the area around your seat. Wipe hard surfaces, and if your seat is leather you can wipe that too. Don't wipe a cloth seat, as the moisture can make germs spread more easily. Follow the instructions on the packaging. And remember, while wiping down the area doesn't hurt, it's not a substitute for proper hygiene. It's more important to wash your hands and avoid touching your face.

When using the lavatory, use paper towels to turn off the faucet and open the door, then throw them away. At your seat, you can use a tissue to touch the touch screen or other controls.

Insurance

One rule of thumb says "only insure what could ruin you". The rationale: why bother to get a policy protecting you on a twenty Euro flight with a no frills carrier? (And chances are, no company would offer such coverage just for that, for anything close to an acceptable rate.) Conversely, be sure you fully understand what could ruin you, e.g., per the discussion in Travel insurance. During travel a long way from home, the costs for an accident or medical emergency (e.g., for treatment, perhaps medical evacuation) really could ruin you. Other unexpected/unforeseen types of events noted in the article could also have serious costs – many times that for a quality policy.

Without your doctor's consultation, even good travel insurance may not cover you if you fail to notify the insurer and airline about health issues. The insurer may levy a surcharge for special coverage, or may not cover complications, e.g., that require unusual medical evacuation. The insurer and some airlines may also require written assurance from your doctor.

See also

• Physical fitness
• Senior travel