Sunburn is a symptom of damaged skin produced by overexposure to the sun, and is a particular danger if you are outside on sunny days, though clouds do not always prevent it. Getting badly sunburnt on the first day of a sun and sand holiday can ruin the rest of your trip.
A related problem is heat stroke, which is not caused exclusively by exposure to the sun, but is dealt with in this article.
- "Mad dogs and Englishmen go out in the midday sun." — Noël Coward
When travelling, you should take care to protect yourself from the sun, as it's common to spend more time outdoors. Never underestimate the power of the sun in tropical regions, the mountains, or even on an ordinary summer day around noontime. Skiing is particularly risky, because aside from direct sun, your body is also hit by sunlight reflected off a smooth, white surface. Similarly, sunlight is reflected by water or sand.
The main danger is from the ultraviolet (UV) part of the sun's radiation; these short-wavelength photons have higher energy than light in the visible part of the spectrum, so they do more damage. UV is not visible to human eyes and can penetrate both light-to-moderate cloud cover and some clothing, so it can be quite difficult to judge how much you are getting; try to err on the side of caution.
A complication is that "ozone holes" in the upper atmosphere, caused by pollution, allow more UV to reach the ground than formerly, so danger in polar regions (under the holes) has risen in recent years. It is not clear how far away from the poles this danger extends, and that may change over time, so anyone spending a lot of time outdoors at high latitude should take precautions.
In addition, sunburns and too much sun over the years can lead to skin cancer. The basal and squamous cell types aren't so bad as far as cancer goes, but their removal will leave unsightly scars. However, melanoma is just as lethal as the other deadly cancers. In the past few decades, it's become known that sunburns substantially increase the risk of melanoma.
Your susceptibility to sunburns is strongly dependent on your skin tone. People with red hair, green eyes and freckled skin are under the highest risk of contracting skin damage. The risk is also increased in spring, before getting used to the stronger light (and similarly, before getting accustomed to stronger sunlight at the destination).
The risk of sunburn increases when the sun is high on the sky (see UV index below). It can also be increased by the intake of pharmaceutical products. Certain antibiotics, contraceptives, tranquillizers, and malaria prophylaxis provoke over-sensitivity to sunshine. Leaving the juice of lemons or other citrus fruit on your skin will increase the rapidity and intensity of a burn.
In recent years, the incidence and severity of sunburn has increased worldwide, especially in the southern hemisphere, because of damage to the ozone layer due to CFCs.
The UV index, as defined by the WHO
The UV index is an international standard that provides information about the intensity of the sun rays and, thereby, potential damage from sunlight on a particular day. The higher the value of the index, the higher the risk for sunburn.
More and more weather stations and local newspapers include a prediction of the UV values for the days to come in their forecast. However, be aware that you will not find this information if you travel to less developed countries. It's wise to get the latest information just before you leave. There are a lot of websites where you can get UV-index predictions from all over the world.
The intensity of UV radiation is affected by the following seven factors:
Angle of the sun
- Latitude – strongest in tropics – specifically, the northern tropics from March 21st to September 21st, and the southern tropics from September 21st to March 21st
- Season – strongest in late spring and early summer assuming no clouds. As this period is quite cloudy in many areas, the peak can be locally pushed back to later in the summer.
- Time of day – strongest from 9 am to 3 pm sun time, peaking at 12 noon. Sun time is more or less reflected in the local time, but as the latter is a political matter it may be off by even some hours. Add one hour where daylight savings is observed (i.e. 10 am to 4 pm). Adjust also for location in the time zone: the sun is early in the eastern edge (subtract half an hour if the zones are regular); later in the west (add half an hour).
These three factors can be combined into one easy measurement. The strongest rays are when the sun is above 45 degrees in the sky. In other words, your shadow is shorter than your actual height. Short shadows mean high UV intensity.
For the mathematically inclined, the general rules for the angle of the sun away from vertical at noon at latitude L are:
- L at the equinoxes, March and October, anywhere.
- L-23° at the summer solstice for your hemisphere, June 21 in the Northern hemisphere and December 21 in the south.
- L+23° at the winter solstice, dates opposite to above.
The tropics are the region where that angle is sometimes zero, L <= 23° so L-23° <= 0 <= L+23°. Between the Tropic of Cancer (23°N) and Tropic of Capricorn (23°S), the sun is sometimes directly overhead.
The midnight sun occurs where L >= 67° so L+23° is sometimes greater than 90° and the midwinter sun is below the horizon even at noon. In summer, the sun is above the horizon even at midnight. Nevertheless, beyond the polar circles where midnight sun occurs, the sun intensity is general so low that everyone but the most hypersensitive can be outdoors around the clock (but take care when there is snow, which will multiply the intensity by reflections, and at high altitudes).
- Altitude – UV radiation increases rapidly with altitude.
- Weather – strongest on clear, dry days (but light clouds give no protection)
- Surroundings – sand, water, and snow reflect UV radiation into shaded areas, and this circumvents UV protection such as hats and umbrellas. And you get the reflected radiation in addition to normal sunlight
- Ozone layer – the ozone layer in the atmosphere gives some protection against UV radiation, but its thickness varies. It is often thinner in the spring near the Arctic and Antarctic, which means more radiation than otherwise also in the temperate zones. These "holes" are not regular.
UV-A and UV-B
The sun emits more than one type of UV radiation. UV-C isn't a problem, as it doesn't make it through the Earth's atmosphere. UV-B is the one that causes what most people think of as sunburn. As its wavelength is short, UV-B only penetrates the uppermost layer of the skin (the epidermis) which therefore absorbs all of the UV-B energy and takes all the damage. Besides causing redness and pain, UV-B also directly damages the skin's DNA and is regarded as the most dangerous type of UV radiation. UV-A goes deeper into the skin and doesn't cause immediate and visible damage. Instead it causes long-term skin damage.
When buying sunscreen, don't choose a version that just protects you from UV-B radiation. Exposure to either type of UV radiation increases the risk for skin cancer.
This is the day when the sun is strongest, and is sometimes called the first day of summer. It occurs on June 21st in the northern hemisphere, and December 21st in the southern hemisphere. Outside the tropics, it could bring the highest level of UV radiation of the entire year. Of course, the atmosphere hasn't had time to fully warm up to the peak of summer yet, and many places are still cloudy and cool. However, if it happens to be sunny, this is the time you need UV protection the most. On the first day of summer, the earth has completed shifting its axis by 23.5 degrees, and that brings tropical-like UV rays to the temperate zones.
- All locations in the tropics have the sun directly overhead at noon twice each year, and on an annual basis receive as much UV radiation as the equator does (assuming equal environmental factors).
- On the summer solstice, locations in the temperate zones (up to 47 degrees latitude) could receive more UV radiation than the equator. Virtually all of Italy, New Zealand, and the eastern United States is below 47 degrees. In the west, the U.S.-Canadian border is at 49 degrees.
- Locations between 47 degrees and the polar circle could receive as much UV radiation on the summer solstice as the tropics do on the other side of the equator (their winter). If it is a clear, sunny day on June 21st in Reykjavík, Iceland, it will have slightly more intense UV rays than Rio de Janeiro. This is due to Reykjavík being closer to the Tropic of Cancer (23.5 degrees north) than Rio.
Fortunately as summer progresses, the earth has re-shifted its axis more in line with the equator. The real danger is that a fair-skinned person who has not been exposed for months spends time out in the sun in the late spring or early summer unprotected. They may mistakenly think the UV radiation is not so bad yet, when in fact, it's even worse.
Before you leave, try to get information on the weather conditions of the region you're traveling to, especially related to sunshine and sun power. The World Health Organization has a table of rough average UV index values for some cities around the world, though for current information you should always check with the local weather forecast service.
When you have arrived at the destination, especially if you're accustomed to places with remarkably less sun intensity, running straight to the beach or taking a three hour stroll in the midday sun in light clothing is something you will regret by bedtime. It takes a couple of days for your skin to get accustomed to the new sun intensity. Even then, follow the advice below.
Sunglasses are a must in bright sunlight, and especially in areas where the surroundings reflect sunlight, such as beaches, glaciers, and deserts.
Make sure your sunglasses leave no gaps in the field of vision: If you gaze downward and can see past the sunglasses, your eyes will still be exposed to some UV radiation. In environments with high UV intensity, such as high altitudes, use ski goggles rather than sunglasses.
Though counter intuitive, clear or light tinted sunglasses offer better protection than dark tinted ones, since a) your natural aversion to sunlight is preserved, and b) your pupils remain constricted, letting less light into your eyes.
Clothing is by far the most effective defence against the sun, but not all clothing is UV resistant, and you can get burnt even while wearing some clothing.
When travelling in a tropical environment, wear a large hat or headscarf, a white or beige long sleeved shirt made of thick cotton, and a pair of long trousers. Avoid wearing shorts and T-shirts; use long-sleeved baggy clothing instead, which will keep you just as cool while avoiding sunburn. The back of your neck is especially prone to sunburn, so get a shirt with a collar and wear the collar upwards (or wear a cotton scarf). Also, protect your face and especially your forehead with a hat or a baseball cap. Wear shoes and socks when possible.
On the beach, don't take your clothing off except when swimming. Of course, in this case, don't stay in the water for too long periods. Consider taking a sunshirt, and other clothing you can wear in the water. If you feel that staying fully clothed defies the whole point of beaches, wrap yourself in a thick sarong while dressed in a swimming costume only.
Do not spend extended time outdoors during the hours around noon without extensive sun protection, especially if you're traveling in the tropics. Use any shade available. Plan outdoor activities (with protection) such as swimming or boating if at all possible in the early morning or late afternoon.
Sun protection lotion
Applying sun protection lotions (sunblock and sunscreen) is better than nothing, but bear in mind that even the highest factor sun lotions only provide partial UV-protection (despite labels claiming "full UVA/B effectiveness"), and none are suitable alone for prolonged (2 hours+) exposure to strong sunlight.
Lotions are rated by SPF, sun protection factor, a measure of how much they reduce burning. For example, if you would burn in ten minutes without protection then with SPF 15 you should be able to go 150 minutes before burning sets in. This is not exact, the effectiveness varies with how thickly the stuff is applied, different countries have different standards for SPF labelling, and the SPF rating generally ignores UV-A radiation which does not cause reddening or pain but may cause other damage. Recent research indicates sun protection factors (SPFs) well above 30 provide little more protection than 30. New FDA standards are to soon be issued (ca Winter 2012) for labeling preparations to better describe what protection they actually offer.
Sun lotions should be thoroughly applied where clothing isn't possible or practicable, e.g., face, on the back of your hands, or on any exposed skin. The tops and bottoms of feet and back of knees can burn surprisingly fast. Waterproof sun protection lotion can be applied if you are planning to stay in the water. To work effectively, preparations need to be reapplied every 2 hours or less, again when in the water or where perspiring. Make sure whatever preparation you use is "fresh". Even the best formulas begin to lose effectiveness after more than a year.
If you get sunburnt, the first symptom is initial redness (erythema), followed by varying degrees of pain, both proportional in severity to the duration and intensity of exposure. After being burned, the skin may turn red 2 to 6 hours later. Pain is worst 6 to 48 hours afterward. The burn continues to develop for 24 to 72 hours after exposure. Skin peeling begins 3 to 8 days after the burn occurs. Common outcomes include tenderness, pain, edema, red and/or peeling skin, rash, nausea and fever. Sunburns may be first- or second-degree burns.
Minor sunburns typically cause nothing more than slight redness and tenderness to the affected area. In more serious cases blistering can occur. Extreme sunburns can be painful to the point of debilitation and may require hospital care.
When seriously burned, try to see a doctor as soon as possible.
Diving into open water to cool off won't help with the burn, and your skin will continue to get damage. Beware of infection if your skin is blistering. Take a cool shower (not cold) or a bath. Avoid scrubbing and shaving, use soft towels to dry yourself.
Get a commercially prepared sunburn cream or Aloe Vera to relieve the immediate symptoms.
Get as much rest as you can and drink lots of water to prevent dehydration. And stay out of the sun until your skin has recovered - which can often take a week or so.
Sunstroke or heat prostration is a life-threatening condition which occurs when the body can no longer control its temperature; body temperature rises and the victim becomes extremely ill.
High ambient temperature is a major factor in this, of course. Humidity is also very important; when the humidity is high, water evaporates more slowly and the body's normal method of cooling itself by sweating is much less effective. Dehydration can contribute to the problem by making you sweat less; you should always drink lots of water when it is hot. Any physical exertion adds to the problem.