The aircraft cabin your health and comfort

The symptoms often described after flying, e.g. dry eyes, taut skin, dry mouth etc. are due to the dry atmosphere on board the aircraft. The relative humidity in most air conditioned buildings is between 40 and 70 per cent which is ideal for comfort. On an aircraft, the relative humidity may be of the order of 20 per cent. This however does not cause true dehydration but these symptoms may be exacerbated by drinking excessive amounts of tea, coffee and alcohol which cause the body to pass more urine. Simple measures such as applying moisturiser and drinking water should alleviate the symptoms. There is no hazard to health as a result of this environment. Contact lens wearers may have to dampen their lenses and should remove them prior to sleeping during the flight.

One of the symptoms often described after flying is dry eyes, this is due to the dry atmosphere on board the aircraft. The relative humidity in most air-conditioned buildings is between 40 and 70 per cent, which is ideal for comfort. On an aircraft, the relative humidity may be of the order of 20 per cent. High water content lenses may dry and distort more than those with lesser water content. This problem may be overcome with gas permeable lenses. Drinking excessive amounts of tea, coffee and alcohol can exacerbate dryness.

Contact lens wearers may have to dampen their lenses and should remove them prior to sleeping during the flight.

Passengers may carry small quantities of liquids, each of which must have a capacity not greater than 100 ml, this includes contact lens solution. You can carry a contact lens case containing fresh lens solution in order that you may remove your lenses should you experience discomfort on the flight, so it is essential that you carry your spectacles in your hand luggage. Although it is perfectly safe to store spare lenses in hold luggage it is not advisable lest the luggage does not appear at your destination.

A blood clot or Deep Venous Thrombosis (DVT), as it is known, can occur in individuals with specific risk factors at any time.

The risk factors for DVT include age greater than 40, previous DVT or blood clot in the lung (pulmonary embolism) or a history of such conditions within the family.

Other factors that are found to be important are hormonal changes associated with pregnancy, the use of the oral contraceptive pill and hormone replacement therapy. Recent surgery or trauma and many forms of cancer can also be associated with increased clotting of the blood.

In addition to these factors, there are some inherited abnormalities of the blood clotting system which may pre-dispose individuals to DVT and pulmonary embolism.

Research by WHO has been published on DVT, which confirms that immobility is an extremely important factor and that being seated for more than four hours in a car, bus, train or an aircraft may increase the risk of blood clotting.

Simple measures may reduce the risk of blood clotting; these include increasing mobility by walking around the aircraft cabin and carrying out simple lower leg exercises that are illustrated in many in-flight magazines.

Drinking adequate amounts of non-alcoholic beverages is important on a long flight, but the routine use of aspirin has not been shown to reduce the risk of clotting which takes place in the veins of the leg. In addition, there is a potential hazard with aspirin and the balance between benefit and harm is not in favour of aspirin and thus its routine use cannot be recommended. However, individuals who may have any of the risk factors outlined should seek medical advice, and it may be that in certain circumstances compression stockings or therapy directed at preventing the clotting process may be appropriate.

If you are unfortunate enough to suffer a DVT associated with travel, the journey home should not be a problem. It is important that any "blood thinning" treatment is stable before travel in order that maximum protection is afforded. It is worth letting the airline know and your treating physician can give details via the MEDIF form.

Why do some airlines carry cardiac defibrillators on their aircraft?

Cardiac arrest is one of the most common causes of sudden death. It is caused by an abnormal heart rhythm which rapidly stops the heart pumping blood round the body. This usually happens during a heart attack, but can also occur with a number of other heart conditions. If a normal heart rhythm cannot be restored in a few minutes, the person will die. It may be possible to keep the person alive by giving them life support (CPR - cardiopulmonary resuscitation), but usually a normal heart rhythm can only be restored by using a heart 'defibrillator'.

The heart muscle has to contract in a regular and coordinated way to pump blood around the body. 'Ventricular fibrillation' is the most common cause of a cardiac arrest and it leads to the heart muscle beating in a completely irregular and uncoordinated way. A defibrillator causes an electrical shock to be passed through the body, which will often change a fibrillating heart to a normally beating one.

The cardiac defibrillators that are carried on aircraft, and are sometimes seen in other public places such as train stations, shopping centres and sports grounds, are known as 'automated external defibrillators' or 'AEDs'. They are very simple to use and once attached to a person are able to automatically detect the heart rhythm and decide if a shock is needed. They are also very safe to use, as they will only allow a shock to be given if it is necessary. Non-medical people can be trained to use them as part of a first aid or life support training course.

Why isn't it compulsory for airlines to carry a defibrillator on an aircraft?

All airlines are legally required to train their cabin crew in first aid and to carry first aid kits on their aircraft. Some airlines have chosen to carry AEDs and to train their cabin crew to use them. However, there is no legal requirement for them to carry defibrillators and some people have suggested that the regulations should be changed to make this compulsory.

Cases of sudden cardiac arrest are very rare when compared to the number of passengers. The evidence from those airlines that have been carrying defibrillators is that although a few lives are saved, in most cases the use of a defibrillator is not successful. This is partly because some of the cases are not due to ventricular fibrillation and a defibrillator will not be able to restore a normal rhythm. Also, even if a normal heart rhythm can be restored, the cause of the abnormal rhythm - such as a heart attack - cannot be treated until the person gets to hospital and this can take several hours.

Although defibrillators are now more commonly found in public places, they are not a legal requirement even in places where large numbers of people gather. There is no evidence that airline passengers are at increased risk of sudden cardiac arrest and most authorities do not consider that it would be justified to make it compulsory for all aircraft to carry defibrillators.

Modern aircraft cabins are pressurised to between 5,000 and 8,000 feet, which causes gas within our body cavities to expand. The body contains air in the middle ear and in the sinuses. As the aircraft climbs, the air expands in the middle ear and flows to the outside via a connection called the Eustachian tube. The air in the sinuses escapes via the nose. On descending, the reverse occurs via the same connections. To assist in this flow of air and avoid pain in the ear or sinuses, it is helpful to periodically swallow, chew or yawn during the descent. Babies often cry, and this has the same effect.

In order that these mechanisms work efficiently, it is not advisable to fly with an infection of the ear, nose or sinuses, as the swelling, which occurs with this infection, can prevent free flow of air and result in pain, bleeding or in the most severe cases, a ruptured ear drum.

Passengers with severe allergies can feel vulnerable when flying due to the theoretical risk of accidental exposure whilst on board. The CAA has commissioned two reports on the topic to better understand the risk of this occurring. The first was from the Health Safety Laboratory (HSL) in 2018. 

A subsequent literature review from Imperial College was then carried out to update this work, as well as to consider ways to prevent it from occurring if necessary. The report covers evidence base for risks and best management of food-allergic individuals on commercial airliners: a systematic review. 

A summary of this work follows:

• The rate of medical events onboard an aircraft is lower than in the non-aviation environment. This may be because of precautions taken by those who travel, such as bringing their own food or notifying the airline in advance of their condition.
• There is evidence to support passengers with allergies wiping down their seat area, tray table and seat-back entertainment system. Some airlines offer pre-boarding to passengers with severe allergies time to allow them the chance to do this.
• When a passenger eats peanuts onboard, the amount that enters the air around them has been shown to be too small to trigger allergic reactions in those nearby.
• Those at risk of anaphylaxis should always carry an adrenaline autoinjector and a spare in their hand luggage. A doctor’s letter is not required to bring these onboard, nor is permission required from your airline. Government guidance is available.
• You should always review your airline’s website in advance of travel to ensure you are aware of their policy relating to food allergies. You may also be able to request alternative catering where this is served onboard.

Separately, a review of anonymised safety reports (MORs) related to allergies onboard UK-registered aircraft over the last 5 years has also been undertaken. The findings from this work are due to be published online in the Journal of Travel Medicine shortly.

Modern commercial aircraft fly at altitudes where the atmosphere outside the aircraft is not able to support human life. All aircraft therefore have systems which ensure that cabin air provides adequate oxygen levels for breathing, as well as removing contaminants and maintaining a comfortable temperature.

On almost all large commercial aircraft the cabin air supply is provided by using some of the outside air which has been drawn into and compressed in the engines. This air, which has very low levels of moisture (humidity), passes through air-conditioning units before being distributed throughout the cabin. The system is automatically controlled to maintain the cabin air pressure at a safe level.

Up to half the cabin air is re-circulated and passes through high efficiency filters, similar to those used in hospital operating theatres, to remove bacteria, viruses and other particles before it is mixed with outside air from the air-conditioning units. Re-circulation helps to increase the moisture level in the cabin air and, because of the use of the high efficiency filters, does not lead to an increased risk of infection.

In recent years some people have expressed concerns about possible health effects due to exposure to contamination of cabin air, particularly contamination of the air drawn from the engines by engine oil. A considerable amount of research has been undertaken in a number of countries and in 2007 the Department for Transport asked the independent Committee on Toxicity to conduct a review of the evidence.

The Committee concluded that the evidence available did not establish a link between cabin air contamination and ill health but made some recommendations for further research. Following additional Government funded research, the Committee reviewed the latest research and published their conclusions in December 2013. The Committee members thought it unlikely that the long-term illnesses that have been reported are linked to a toxic effect of cabin air contamination. You can read the full report on the Independent Committee of Toxicity's website.

Further information and cabin air quality data

The process of disinfection is required under the International Health Regulations of the World Health Organization (WHO) on flights to and from certain destinations to prevent infectious and contagious diseases. These rules permit the use of insecticides, which are recommended by the WHO based on their effectiveness and safety.

Further information may be found on the World Health Organization Website.

Most contagious illnesses, such as chicken pox, measles, 'flu or the common cold, are spread as a result of close contact between people. This most commonly happens through 'droplet spread' - breathing in viral particles or bacteria carried into the air when someone with the illness coughs or sneezes close by.

You might pick up an infection on the aircraft if someone in a seat close to you has a cold or other contagious disease. However, it is just as likely that you could catch an infection from someone close to you when travelling by public transport, at the airport, in your hotel or at a conference - indeed anywhere where you might be in close contact with other people.

You may have heard that you are more likely to catch an infection on board an aircraft because some of the cabin air is re-circulated. However, the air that is re-circulated passes through filters which are highly effective at removing particles, including bacteria, viruses and fungi that can cause infection. Research has shown that you are no more likely to catch an infection on an aircraft that has re-circulated air than on one where the air is not re-circulated.

I have been diagnosed as having an infection which is contagious (an infection that may be passed from one person to another). I am due to fly soon, what should I do?

You should delay your flight until the illness is no longer contagious. Talk to the doctor who is treating you to find out when you will be able to travel.

If possible, arrange to get a letter from the doctor once you are no longer contagious, confirming this and that you are fit to fly. This can be particularly important for some illnesses, such as chicken pox, where you may still have some signs of the illness such as a spots or a rash. The airline may refuse to let you travel if the staff at the airport or on the aircraft think that you may still be contagious.

It is advisable to inform the airline that you are due to fly with, as they will be able to tell you if they have any specific requirements such as a letter from your doctor before they will let you travel. They will also tell you if there will be any additional charges if you have to change your booking. You should also contact your insurer if you have travel insurance, as you may be able to make a claim if you have to pay to re-book your flight or have to cancel the flight or a holiday because of your illness.

Should I fly if I have recently been in contact with a person who has a contagious disease (an infection that may be passed from one person to another)?

You should talk to your doctor and let them know that you are intending to fly. The doctor will be able to tell you how likely it is that you will develop the illness, how long it usually takes for someone to become unwell if they do catch the infection and what you should do if you develop symptoms.

For most infections you are only likely to be contagious (able to pass on the disease) once you have symptoms of the illness. If you are feeling well and do not have any signs of illness, such as a rash or a cough, you will probably be able to travel.

Don't forget to check that you have travel insurance cover, in case you become unwell and need medical treatment while you are away.

Why do I always pick up an infection after I have travelled in an aircraft?

Most contagious illnesses, such as chicken pox, measles, 'flu or the common cold, are spread as a result of close contact between people. This most commonly happens through 'droplet spread' - breathing in viral particles or bacteria carried into the air when someone with the illness coughs or sneezes close by.

You might pick up an infection on the aircraft if someone in a seat close to you has a cold or other contagious disease. However, it is just as likely that you could catch an infection from someone close to you when travelling by public transport, at the airport, in your hotel or at a conference - indeed anywhere where you might be in close contact with other people.

You may have heard that you are more likely to catch an infection on board an aircraft because some of the cabin air is re-circulated. However, the air that is re-circulated passes through filters which are highly effective at removing particles, including bacteria, viruses and fungi that can cause infection. Research has shown that you are no more likely to catch an infection on an aircraft that has re-circulated air than on one where the air is not re-circulated.