Altitude Sickness & Exposure

Staying Healthy

1. Exposure to Cold

The major risks to people exposed to the cold are: general body cooling leading to hypothermia (exposure), and local cooling, primarily affecting the hands and feet (chilblains & frostbite). Those at greatest risk are the ill-prepared.

Visitors to cold climates should be aware of the condition known as hypothermia which is caused when a person’s internal body temperature falls below normal (37C). It is likely to happen on cold, wet, windy days to people who are poorly clothed, hungry and tired.

Cold conditions are exacerbated by wind where the temperature is effectively lowered and it appears to be much colder than it actually is. This phenomenon is known as wind-chill.

2. Frostbite

Frostbite is the freezing of the skin and surrounding tissues and can occur in anyone exposed to temperatures below freezing without adequate protection. Frostbite should never be defrosted if there is a likelihood of re-freezing as this will greatly exacerbate the problem.

Chilblains (non-freezing cold injury) occur in cold, damp conditions where the hands and feet are cold (and generally wet) for extended periods. They are characterized by itchy or painful swellings that can lead to open sores if left untreated.

3. Hypothermia

Hypothermia is a dangerous condition and is often accompanied by mental confusion where the person affected does not realize what is happening preventing them from seeking help. Extreme hypothermia can lead to death in just a few hours.

Prevention of hypothermia is achieved by the use of appropriate clothing including hats, gloves/mittens, suitable socks, and boots. There is an abundance of excellent protective clothing available for outdoor enthusiasts. Specialist advice should be sought as to the best equipment for a trip, including survival equipment. Loss of articles of clothing in an accident can be disastrous unless spares are carried.

Symptoms of hypothermia

  • Uncontrolled shivering followed by
  • Confusion & dizziness
  • Slow, clumsy movements and difficulty in walking
  • The person feels tired
  • Breathing becomes shallow and the pulse becomes slow
  • Loss of consciousness


Prevention of these conditions is achieved by maintaining adequate insulation from the cold by the use of appropriate clothing, keeping the extremities warm and dry, and by consuming high-energy foods and warm drinks.

Being attentive to early signs and symptoms is important. If frostbite is suspected the casualty should be referred for medical help as soon as possible.


Treatment of someone suffering from hypothermia entails preventing any further drop in body temperature. This involves seeking shelter, insulating, and protecting them from the cold environment. Replace any wet clothing with dry ones. Make sure the head, feet, and hands are covered. Place the person in a sleeping bag with another person. Give them warm drinks and high-energy foods (sweets, chocolate, etc.) Avoid rapid re-warming unless the victim is well and conscious.

4. Sun Exposure

Everybody seems to like sunny weather. Sunlight is a source of natural light and energy. It is good for our general health, has healing properties, and produces a feel-good factor. Although sunbathing may be enjoyable it must always be remembered that excessive exposure to the sun’s rays is a health hazard due to the harmful effects of ultraviolet radiation on the skin.

The sun emits two kinds of ultraviolet rays:

UVA – which penetrates deeply into the skin and can trigger allergies and cause premature aging and wrinkling.

UVB – these affect the upper layers of the skin and trigger the production of melanin which causes tanning. Too much causes burning, freckling, and thickening of the skin. They can also cause skin cancers.

Who’s at risk?

  1. Fair-skinned people who very often have red or white hair and blue eyes.
  2. Those persons with certain medical conditions such as albinism, lots of moles, or previous skin cancer.
  3. Those on certain medications such as tetracyclines or diuretics.
  4. People with certain skin conditions such as psoriasis, eczema, and vitiligo need to take special care when they are in the sun.
  5. The elderly, babies, and young children are particularly sensitive.

Preventative measures

  • Everyone should avoid the midday sun, usually from noon until 2 pm (3 pm in the tropics).
  • Adults should wear broad-brimmed hats, long-sleeved shirts, and sunglasses. Children should wear long-sleeved shirts, hats, and high-factor waterproof sunscreen.
  • Babies under 9 months should be kept out of direct sunlight.
  • Never lie in the sun to dry off after swimming, the skin will burn in a matter of minutes.
  • High altitude climbers etc. should wear a hat with a neck cover and sunglasses with nose shields and blinker side pieces.
  • Wear cotton fabrics next to the skin, they are cooler. Avoid loose weave fabrics that allow penetration of the sun’s rays.

5. Sunburn

Sunburn often affects skiers, climbers, and trekkers at high altitudes where the intensity of the light increases by stealth. The higher the altitude, the more concentrated the sun’s UV rays. Each 300-meter gain in altitude adds 4% to the sun’s intensity.

The sun’s rays can also penetrate through water and are effectively magnified. In shallow water, the rays can reflect off a sandy bottom. Therefore, being underwater can be deceptive due to the cooling effect of the water.

Snorkelers should always wear a tee shirt or similar to prevent the sun from burning their backs. Scuba divers are not normally at risk due to their protective clothing and they are often too deep for harmful UV penetration.

Sunburn, when it occurs, is a major cause of distress to travelers and can have long-term effects including skin cancer and premature skin aging. Overexposure to the sun can also dehydrate the skin.


Sun factor preparations work by reducing or blocking the effects of sunlight allowing a person to stay in the sun longer. Everyone who intends to expose themselves to direct sunlight should consider using a preparation with an appropriate Sun Protection Factor.

These absorb ultraviolet B (UVB) and to a lesser extent ultraviolet A (UVA).

The Sun Protection Factor (SPF) refers to the protection against UVB and will be marked on the outside of the container. Factors range from 2 to as high as 50.

With no protection, most people’s skin will start to burn after 10 minutes of exposure to the sun. The sun protection factor allows you to sunbathe longer in safety without burning e.g. An SPF 8 allows approximately 8 times longer sun exposure, an SPF 15 allows 15 times longer, etc.

Always re-apply preparations after swimming, even if they are waterproof. The effectiveness of the protection will always decrease after immersion in water.

Snorkelers should always wear a tee shirt or similar to prevent the sun from burning their backs. Scuba divers are not normally at risk due to their protective clothing and they are often too deep for harmful UV penetration.

Sunburn, when it occurs, is a major cause of distress to travelers and can have long-term effects including skin cancer and premature skin aging. Overexposure to the sun can also dehydrate the skin.


These preparations are based on zinc oxide or titanium dioxide and are applied thickly to particularly sensitive areas like the lips and nose. They block out the sun’s harmful rays by forming a reflective barrier.

They are particularly useful for persons going to high altitudes where the rays are more intense and are also popular with certain sportspeople such as cricketers who spend long periods in the sun.

Treatment of sunburn

  1. Get the person out of the sun.
  2. Cool the skin where possible with cold running water, a cold shower, or immersion in a cool to a lukewarm bath.
  3. Avoid direct pressure on the burnt area.
  4. Give pain killers.
  5. Apply calamine lotion, witch hazel, or a proprietary after sun lotion. After-sun is very effective at cooling, calming, and moisturizing the skin, it will also help to prevent peeling.

6. Hyperthermia

This condition occurs when the body is unable to cool its core temperature sufficiently and overheats. It is manifest in two distinct ways:

  1. Heat Exhaustion
  2. Heat Stroke

Heat exhaustion

Heat exhaustion is characterized by:

  • Headache dizziness and nausea
  • Cramps in the limbs and/or abdomen
  • Profuse sweating with pale, clammy skin
  • Rapid, weak breathing and pulse

When someone is suffering from heat exhaustion, try to cool them down by removing them from direct sunlight into the shade. Lie them down and apply lukewarm (not cold) water with a sponge or similar. They should be encouraged to drink as much rehydration solution as they can take. Allow them to rest until they fully recover, monitoring closely for any signs of deterioration.


Heatstroke is a serious condition caused by a failure of the body’s natural thermostat resulting in an inability to cool itself down by normal means. It usually occurs as a result of exposure to very hot surroundings. The onset can be sudden, resulting in unconsciousness in a matter of minutes. Medical assistance should be sought as soon as possible.

The main signs of heatstroke are:

  • Headache, dizziness, confusion & restlessness
  • Hot, flushed, dry skin due to failure of the sweating mechanism
  • A full, bounding pulse
  • Body temperature above 40C
  • Rapid deterioration in the level of response
  • When heat stroke occurs the main priority is to cool the patient down as quickly as possible but never use ice or very cold water to avoid thermal shock which could kill them.

Remove the patient from any heat source and wrap them in a cool, wet sheet and keep them well ventilated. Make sure the sheet remains wet. Monitor closely for signs of cardio-respiratory failure and be prepared to resuscitate if necessary. When the temperature drops below 38C the wet sheet can be removed but if their temperature begins to rise again, replace it and continue as before.

7. Altitude Sickness

The pleasures of trekking in the world’s highest mountain ranges cannot be overstated. Neither can the dangers. Altitude sickness can occur in some people as low as 8,000ft, but serious symptoms do not usually occur until over 12,000ft. Even then it is not the height that is important, but rather the speed at which you ascended to that altitude.

Acute mountain sickness (AMS) is actually more common in fit young men because they are more likely to attempt a rapid ascent by racing up the mountain like some indestructible superhero! As a general rule, it is far safer (and more enjoyable) to avoid altitude sickness by planning a sensible itinerary that allows for gradual acclimatization to altitude as you ascend, (you can race back down as fast as you like!).

Causes of altitude sickness

The percentage of oxygen in the atmosphere at sea level is about 21% and the barometric pressure is around 760 mmHg. As altitude increases, the percentage remains the same but the number of oxygen molecules per breath is reduced. At 3,600m (12,000ft) the barometric pressure is only about 480 mmHg, so there are roughly 40% fewer oxygen molecules per breath so the body must adjust to having less oxygen.

In addition, high altitude and lower air pressure cause fluid to leak from the capillaries in both the lungs and the brain which can lead to fluid build-up. Continuing on to higher altitudes without proper acclimatization can lead to potentially serious, even life-threatening altitude sickness.

How high does it start affecting me?

It is difficult to determine who may be affected by altitude sickness since there are no specific factors such as age, sex, or physical condition that correlate with susceptibility. Some people get it and some people don’t because some people are more susceptible than others.

Most people can ascend to 2,500m (8,000ft) with little or no effect. If you have been at that altitude before with no problem, you can probably return to that altitude without problems as long as you are properly acclimatized. If you haven’t been to high altitudes before, you should exercise caution when doing so.

Chances of getting it:

Unikely: under 2,500m (8,000ft)
High: 2,500m – 4,000m (8,000ft – 13,000ft)
Very High: 4,000m – 5,500m (13,000ft – 18,000ft)
Extremely High: over 5,500m (18,000ft)

Acute Mountain Sickness (AMS)

AMS is very common at high altitudes. At over 3,000m (10,000ft) 75% of people will have mild symptoms. The occurrence of AMS is dependent upon the elevation, the rate of ascent, and individual susceptibility. Many people will experience mild AMS during the acclimatization process. The symptoms usually start 12 to 24 hours after arrival at altitude and begin to decrease in severity around the third day.

Early symptoms of AMS include:

  • Headache
  • Nausea & Dizziness
  • Loss of appetite
  • Fatigue
  • Shortness of breath
  • Disturbed sleep
  • A general feeling of malaise

The signs and symptoms of Moderate AMS include:

  • Severe headache that is not relieved by medication
  • Nausea and vomiting, increasing weakness and fatigue
  • Shortness of breath
  • Decreased coordination (ataxia)

Signs of severe AMS:

  • Inability to walk
  • Decreased mental state
  • Fluid build-up in the lungs

There are two serious conditions associated with severe altitude sickness; High Altitude Cerebral Oedema (HACO) and High Altitude Pulmonary Oedema (HAPO). Both of these happen less frequently, especially to those who are properly acclimatized. But, when they do occur, it is usually in people going too high too fast or going very high and staying there. In both cases, the lack of oxygen results in leakage of fluid through the capillary walls into either the lungs or the brain.

High Altitude Pulmonary Oedema (HAPO)

HAPO results from fluid buildup in the lungs. This fluid prevents effective oxygen exchange. As the condition becomes more severe, the level of oxygen in the bloodstream decreases, which leads to cyanosis, impaired cerebral function, and death.

In cases of HAPO, immediate descent of around 600m (2,000ft) is a necessary life-saving measure. Anyone suffering from HAPO must also be evacuated to a medical facility for proper follow-up treatment.

High Altitude Cerebral Oedema (HACO)

HACO is the result of the swelling of brain tissue from fluid leakage.
It generally occurs after a week or more at high altitudes. Severe instances can lead to death if not treated quickly. Immediate descent of around 600m (2,000ft) is a necessary life-saving measure. There are some medications that may be used for treatment in the field, but these require proper training in their use.

Anyone suffering from HACO must be evacuated to a medical facility for follow-up treatment.


  1. If possible, don’t fly or drive at high altitudes. Start below 3,000m (10,000ft) and walk up
  2. If you do fly or drive, do not overexert yourself or move higher for the first 24 hours
  3. If you go above 3,000m (10,000ft), only increase your altitude by 300m (1,000ft) per day, and for every 900m (3,000ft) of elevation gained, take a rest day to acclimatize
  4. Climb high and sleep low! You can climb more than 300m (1,000ft) in a day as long as you come back down and sleep at a lower altitude
  5. If you begin to show symptoms of moderate altitude sickness, don’t go higher until symptoms decrease
  6. If symptoms increase, go down, down, down!
  7. Keep in mind, that different people will acclimatize at different rates. Make sure everyone in your party is properly acclimatized before going any higher
  8. Stay properly hydrated. Acclimatization is often accompanied by fluid loss, so you need to drink lots of fluids to remain properly hydrated (at least four to six liters per day). Urine output should be copious and clear to pale yellow
  9. Take it easy and don’t overexert yourself when you first get up to altitude. But, light activity during the day is better than sleeping because respiration decreases during sleep, exacerbating the symptoms
  10. Avoid tobacco, alcohol, and other depressant drugs including, barbiturates, tranquilizers, sleeping pills, and opiates such as dihydrocodeine. These further decrease the respiratory drive during sleep resulting in a worsening of symptoms
  11. Eat a high-calorie diet while at altitude
  12. Remember: Acclimatization is inhibited by overexertion, dehydration, and alcohol


The main cause of altitude sickness is going too high too quickly. Given enough time, your body will adapt to the decrease in oxygen at a specific altitude. This process is known as acclimatization and generally takes one to three days at any given altitude, e.g. if you climb to 3,000m and spend several days at that altitude, your body will acclimatize to 3,000m. If you then climb to 5,000m your body has to acclimatize once again.

Several changes take place in the body which enable it to cope with decreased oxygen:

  • The depth of respiration increases
  • The body produces more red blood cells to carry oxygen
  • Pressure in pulmonary capillaries is increased, “forcing” blood into parts of the lung that are not normally used when breathing at sea level
  • The body produces more of a particular enzyme that causes the release of oxygen from hemoglobin to the body tissues

Please Note: There is NO substitute for proper acclimatization!!


The only cure for mountain sickness is either acclimatization or descent.

Symptoms of Mild AMS can be treated with pain killers for headaches, acetazolamide, and dexamethasone. These help to reduce the severity of the symptoms, but remember, reducing the symptoms is not curing the problem and could even exacerbate the problem by masking other symptoms.

Acetazolamide allows you to breathe faster so that you metabolize more oxygen, thereby minimizing the symptoms caused by poor oxygenation which is especially helpful at night when the respiratory drive is decreased.

Dexamethasone: This powerful steroid drug can be life-saving in people with HACO, and works by decreasing swelling and reducing the pressure in the skull. The dosage is 4 mg three times per day, and obvious improvement usually occurs within about six hours. This drug “buys time” especially at night when it may be problematic to descend. The descent should be carried out the next day. It is unwise to ascend while taking dexamethasone: unlike Diamox, this drug only masks the symptoms.

The Gamow Bag

This clever invention has revolutionized the field treatment of altitude sickness. The bag is composed of a sealed chamber with a pump.

The casualty is placed inside the bag and it is inflated by pumping it full of air effectively increasing the concentration of oxygen and therefore simulating a descent to a lower altitude.

In as little as 10 minutes the bag can create an “atmosphere” that corresponds to that at 900 to 1,500m (3,000 to 5,000ft) lower. After two hours in the bag, the person’s body chemistry will have “reset” to the lower altitude.

This acclimatization lasts for up to 12 hours outside of the bag which should be enough time to get them down to a lower altitude and allow for further acclimatization.

The bag and pump together weigh about 6.5kg (15lb) and are now carried on most major high altitude expeditions. Bags can be rented for short-term treks or expeditions.

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