Sunburn in Southeast Asia poses a greater hazard to unprotected visitors than monkey bites or bedbugs. Most of the countries in Southeast Asia are close to the equator, and also experience their peak tourist seasons during the sunniest months.
And - unlike monkeys or bedbugs - the sun is everywhere. (At least during the day.)
The tips below are intended to show you why you should protect yourself, and how to best make sure you don't fly home roasted worse than a turkey on Thanksgiving.
To find out about the ill effects of UV exposure, read this primer on UV Radiation.
Southeast Asia's High UV Radiation Levels
Tourists from temperate countries may not understand just how much sun they can expect to get when visiting Southeast Asia. The answer is, a lot. A number of factors converge to make Southeast Asian countries among the worst places to be caught out of doors without sun protection.
Let's start with latitude and altitude. Simply put, the less atmosphere there is between you and the sun, the worse the sun's effects will be. In temperate regions, sunlight travels at a more oblique angle relative to the atmosphere - with more air in the way, less ultraviolet light reaches the ground.
In tropical regions (like most of Southeast Asia), sunlight at noon is almost exactly at a perpendicular angle to the earth.
There's less atmosphere in the way to dissipate UV light, and any unprotected visitors in the open are more likely to be burned.
The same equation holds for places at higher altitudes - since the atmosphere is thinner on mountain trekking trails, for instance, trekkers will get a higher degree of UV exposure than their counterparts at sea level.
According to the Mountaineering Handbook, the sun increases in intensity by four percent for every 1,000 feet (300 meters) increase in altitude.
Seasons also play a role in determining UV intensity, but less so in Southeast Asia compared to more temperate regions. The closer you are to the equator, the less variation you get in UV intensity from season to season, although UV intensity is generally high all year round.
A look at the World Health Organization's worldwide UV measurements tell us that equatorial countries like Singapore (1°N) experience a high UV index number of 13 in March and April… and a decrease of only three units at its lowest point in December. Cities like Hanoi in Vietnam (21°N) experience a high UV index number of 12 in July and August, with lows of 6 from November to January.
About the UV Index
The UV Index is a measurement system devised by the National Weather Service and the U.S. Environmental Protection Agency (EPA) to measure UV radiation intensity.
The number reflects the high point of UV intensity during the day (typically noontime), and is calibrated on a scale of 1 to 11+. 1-2 is regarded as "low", while values higher than 11 are called "extreme". UV indexes in Southeast Asia vary from high moderate to extreme.
For Moderate readings of 3 to 5, you'll need to wear UV-blocking clothing (hat, sunglasses, UV-resistant garments), and sunscreen if you're going to be outdoors for over thirty minutes. Seek shade at midday.
For High and Very High readings of 6-10, you'll have to reduce or avoid sun exposure between 11am and 4pm, and wear UV-blocking clothing at all times.
For Extreme readings of 11 and above, you'll have to go the full monty: avoid sun exposure between 11am and 4pm, wear UV-blocking clothing at all times, and avoid bright surfaces that can reflect UV radiation (white sand, tile, seawater).
How to Protect Yourself
If you don't take precautions beforehand, you're sunk - it's not that easy to find cheap sunblock or effective UV-resistant clothing at the last minute in most places in Southeast Asia, especially if you're somewhere off the beaten track.
The simplest precaution to take: minimize time spent in the sun. Go indoors when the sun reaches the highest point in the sky - from 10am to 3pm.
Keep in mind that sunlight won't just strike from the direction of the sun, but is also reflected upward from seawater and white sand. If you're the shade, but you're anywhere near the glare of the beach or a swimming pool, you can still get burned.
Sunscreen lotions, creams, sprays, and gels contain ingredients that absorb certain UV wavelengths, thus protecting the skin from UV damage to varying degrees.
Each sunscreen product is assigned a sun protection factor (SPF), a number that refers to the relative sunburn protection offered by the product. An SPF of 15 means that it would take 15 times longer for a user to get sunburned, compared to the time it takes to get sunburned without using the product. If one's unprotected skin gets sunburned after 20 minutes' sun exposure, for instance, adding an SPF 15 sunscreen extends that time to five hours.
It's recommended you get sunscreen with SPF of no lower than 40 if you're planning to go to Southeast Asia during the summer months.
Cover up as much as you can without overheating your body. Wear a wide-brimmed hat for your face and head; sunglasses to protect your eyes from glare; and UV-resistant clothes that protect your shoulders, arms, and legs. Loose-weave fabrics are terrible at blocking UV rays, while certain fabrics are specially formulated to block UV.