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Air travel and your health
Air travel in Australia is a massively popular activity nowadays. As of 2015, Australian airports see about 34 million arrivals and departures, a rise of nearly 1.5 times, within the last 10 years. 
Modern air travel is remarkably safe, and normally poses no significant challenges to your health. Overall, travelling can be fun, and most people don't get sick. However, travelling by air does come with an increase in some health risks. Knowing what to look out for, and following the advice given below, can help you avoid these risks. If you do get sick, rest up, keep up your fluids and consider seeing your doctor.
Why we get sick from air travel
There are several aspects of air travel that can impact your body:
Time zones, stress and fatigue
The human body was not made to jump thousands of miles within a few hours; our bodies become confused when they move across time zones and days change their length. In addition, the preparations for flight (arriving at the airport on time, going through airport security, taking care of baggage, passports, tickets, etc.) can cause you stress and tire you out,
The air in an aeroplane's cabin contains about 10% less oxygen than usual. This is usually not a problem for healthy people, but can increase the risk of headaches, nausea and other ailments. This is especially true for young children and people with certain medical conditions, including heart, lung and circulation problems.  
Air pressure inside the cabin of an aeroplane is also lower than normal. This causes any air found inside your body to expand. Normally this will not be a problem, but it can pose a risk to people with heart, lung and circulation problems (as above), and also to people who are recovering from recent surgery, especially eye, ear or brain surgery. A surgical procedure can often result in small 'air pockets' forming in the area. These pockets gradually disappear in the days and weeks after surgery, but if you fly, they are in danger of bursting.
At usual flying altitudes, the air is usually at least 10% drier than normal. Dry air dries up the delicate linings of our nose and throat, making them prone to infections.
People on flights, especially long-haul flights, find themselves sitting for long periods of time without much room or opportunity to move or stretch.
Deep vein thrombosis
A deep vein thrombosis (DVT) is when a blood clot forms within a deep vein, usually in the calf or thigh. If a clot becomes dislodged it can cause serious injury, including a pulmonary embolism that blocks the movement of blood from the heart to the lungs. DVT is associated with inactivity: when your muscles don't move, blood moves more slowly through your veins and can form a clot more easily.
Flying increases the risk of DVT, because flying usually involves long periods of sitting down. Any flight over four hours, or taking a number of flights close together, may put you at risk.
You can reduce the risk of getting DVT on your flight by drinking lots of fluids, stretching your legs and walking around the cabin at regular intervals throughout the flight. Compression stockings can also be worn on your lower legs, to reduce the risk of developing a DVT. Check our report on DVT for ways to lower your risk of DVT.
People flying shortly after surgery are at particular risk of DVT, as they are more prone to inactivity before and during their flight home.
During a flight, you are in constant motion, which can be disorienting to some. To reduce the effect of motion sickness if you are particularly prone to it: fly at night, adjust your seat to recline when this is allowed; ask your flight company to sit you near the plane's centre; consider medications to reduce motion sickness.
Hygiene and infection
Anecdotally, many people swear they get sick every time they travel on a plane. Some even term it the 'aeroplane cold'. One study found that people travelling on planes were at least five times more likely to catch a cold. 
Some small studies have identified the cause of this. The air quality on planes is sufficiently clean thanks to constant recirculation and filtration. However, despite stringent hygiene standards, aeroplanes are a potential incubator for viruses and bacteria, which can survive on surfaces for several hours. The toilet, which is shared on average by 50 people, can harbour many sources of infection. Other surfaces such as tray tables, pillows, blankets and magazines, are also potential contamination sites.
In addition, long-haul flights, travel-related stress and high altitudes can tire the body. Fatigue leads to an increased susceptibility to catching a cold (or other infections). The constant noise and vibration can also add to the stressful environment.
How to deal with air travel
Before you fly
- Rest up before flying;
- Avoid travelling if you or a family member are sick;
- Make sure that your vaccinations are up to date, and;
- Plan your sleep schedule so you get a good amount of sleep around your travel.
During your flight
- Keep hydrated - drink plenty of water;
- Avoid alcohol, as it can dehydrate you and can cause more disturbed sleep patterns;
- Keep hands and surfaces clean with sanitary wipes and washes;
- Open your overhead air vent to recirculate your air;
- Change seats so you are not sitting next to or near someone who is sick;
- It is best to avoid sitting in the aisle seat, as people frequenting the toilet tend to contaminate aisle seating (with planes increasingly filled to capacity it may not be possible to change seats but it is worth trying), and;
- Avoid using airline pillows and blankets - bring your own.
After you land
- Rest up to prevent jetlag;
- Keep yourself hydrated;
- Try to find time to be physically active. Exercising - even going for a short walk - can help your body recover and adjust, and;
- Be careful to not catch infections at the airport, such as at check-in kiosks or baggage areas.
Many women end up travelling during this period, as they may not yet know that they are pregnant, or do not want to delay travel plans organised before pregnancy occurred.
The first trimester of pregnancy can be hard on many women. Morning sickness, motion sickness, tiredness, and the need to go to the toilet frequently are not easy anywhere, and doubly so during travel. That said, some women feel fine (or nearly so) at this point and have no trouble travelling.
In addition, the first trimester is the most likely time for a miscarriage to occur. Flying does not add to the risk of miscarriage, but having a miscarriage while travelling can be an upsetting experience.
Air travel is normally considered safe during the first trimester unless your pregnancy is considered high-risk. Consult your doctor if you are concerned.
During the flight itself:
- Drink plenty of (non-alcoholic, uncaffeinated) liquids to avoid dehydration, and;
- Get up frequently and move around. Pregnancy and air travel are both risk factors for blood clots and DVT, and walking can lower that risk. Ask for an aisle seat to make it easier. An aisle seat will also help you get to the toilet more easily.
This is considered the best time to travel as long you are having a low-risk pregnancy and your doctor has given you the go-ahead.
Now may not be the best time to travel, due to the obvious physical constraints of your pregnancy such as a large belly, your ankles swelling up during travel, feeling uncomfortable sitting for long periods, needing the toilet often and getting tired quickly.
Be aware that many airlines will not allow you to fly if you are 28 weeks pregnant or more, but this varies - check before you book.
People with existing medical issues
Air travel can become riskier or more complicated for people with certain medical conditions. Ask your doctor for advice on flying if you:
- Have been diagnosed with psychosis, unless it is fully controlled;
- Plan to take a baby under 48 hours old on the flight;
- Have any infectious conditions;
- Have sickle-cell anaemia, angina or chest pain at rest;
- Have unresolved pneumothorax;
- Are recovering from a recent stroke, heart attack or surgery where air pockets may be present;
- Are recovering from recent eye surgery, especially after an eyeball injury;
- Are recovering from recent brain surgery or brain infection, trauma or haemorrhage, or;
- Have nasal, sinus or inner-ear infections and blocked eustachian tubes.
For people with diabetes, the disturbance of their regular mealtime schedules can make it hard to keep track of their glucose levels. While some prefer calculating their insulin schedule in advance, others might benefit more from checking their blood glucose levels more frequently during their travel, and managing their insulin accordingly.
If you have epilepsy, make sure you carry enough anti-epileptic medications to last you through the flight, including any unforeseen delays. Be sure to wear your identification bracelet.
If you have been scuba diving, you may need to allow a certain amount of time between your last dive and flying home. This is because excess nitrogen gas can stay dissolved in your body for some time after diving. The low atmospheric pressure during air travel increases the risk of developing decompression sickness. The recommended amount of time to wait before flying will depend on the length and depth of your dives.
If you are taking any medications, keep them in your carry-on baggage, not with your checked baggage, in case your bags are misplaced during travel.
Children can sometimes be particularly prone to the health risks mentioned above, particularly infections.