Frequently Asked Questions
Learn more about UV, sun protection, skin, sunscreen products and more…
Ultraviolet (UV) radiation is part of the electromagnetic spectrum emitted by the sun.
Whereas UVC rays (wavelengths of 100-280 nm) are absorbed by the atmospheric ozone, most radiation in the UVA range (315-400 nm) and about 10 % of the UVB rays (280-315 nm) reach the Earth’s surface. Both UVA and UVB are of major importance to human health.
Small amounts of UV are essential for the production of vitamin D in people, yet overexposure may result in acute and chronic health effects on the skin, eye and immune system.
Environmental factors that influence the UV level:
- Sun height—the higher the sun in the sky, the higher the UV radiation level. Thus UV radiation varies with time of day and time of year, with maximum levels occurring when the sun is at its maximum elevation, at around midday (solar noon) during the summer months.
- Latitude—the closer the equator, the higher the UV radiation levels.
- Cloud cover— UV radiation levels are highest under cloudless skies. Even with cloud cover, UV radiation levels can be high due to the scattering of UV radiation by water molecules and fine particles in the atmosphere.
- Altitude—at higher altitudes, a thinner atmosphere filters less UV radiation. With every 1000 metres increase in altitude, UV levels increase by 10% to 12%.
- Ozone—ozone absorbs some of the UV radiation that would otherwise reach the Earth’s surface. Ozone levels vary over the year and even across the day.
- Ground reflection—UV radiation is reflected or scattered to varying extents by different surfaces, e.g. snow can reflect as much as 80% of UV radiation, dry beach sand about 15%, and sea foam about 25%.
The UVI (UV index) is a measure of the level of UV radiation.
The values of the index range from zero upward – the higher the UVI, the greater the potential for damage to the skin and eye, and the less time it takes for harm to occur.
The UVI is an important vehicle to alert people about the need to use sun protection.
Effects on skin
The skin’s sensitivity to the sun can be classified according to the phototype (the lighter the skin, the more it is necessary to protect itself from the sun) as in the following illustration:
- Phototype I
- Reaction to the sun: does not tan, systematically catches sunburn.
- Type: very light skin, freckles, blond or red hair.
- Phototype II
- Reaction to the sun: tans with difficulty, often gets sunburn.
- Type: very light skin, blond or brown hair, freckles appear in the sun, clear eyes.
- Phototype III
- Reaction to the sun: sometimes has sunburns, tans gradually.
- Type: fair skin, blond or brown hair.
- Phototype IV
- Reaction to the sun: catches few sunburns, tans quickly.
- Type: dark skin, brown, brown or black hair, dark eyes.
- Phototype V
- Sun reaction: rarely gets sunburned, tans quickly.
- Type: dark skin, dark eyes, dark hair.
- Phototype VI
- Reaction to the sun: dark skin, never gets sunburned.
- Type: black skin, black hair.
In small quantities UV radiation is beneficial and essential for the synthesis of vitamin D.
UV rays are also used to treat several diseases, including rickets, psoriasis, eczema and jaundice. These are treatments performed under medical supervision and the weighing of the advantages of these compared to the risks of UV exposure is a matter of clinical appreciation.
Finally, the sun has a positive effect on our mood and our morale while allowing to have a tanned skin.
In humans, prolonged exposure to UV radiation can have acute and chronic skin, eye and immune effects.
Sunburn (erythema) is the best known acute effect of excessive UV exposure. In the long term, UV rays cause degenerative damage in skin cells, fibrous tissue and blood vessels, leading to premature aging of the skin, photodermatoses and actinic keratoses. is the best known acute effect of excessive UV exposure.
Another long-term effect is the inflammatory reaction of the eye. In the most severe cases, skin cancer or cataracts can appear.
Simple precautions in the sun
Adopting the following simple precautions can make all the difference knowing that experts believe that four out of five cases of skin cancer could be prevented, as UV damage is mostly avoidable:
- Limit time in the midday sun
The sun’s UV rays are the strongest between 10 a.m. and 4 p.m. To the extent possible, limit exposure to the sun during these hours.
- Watch for the UV index
This important resource helps you plan your outdoor activities in ways that prevent overexposure to the sun’s rays. While you should always take precautions against overexposure, take special care to adopt sun safety practices when the UV Index predicts exposure levels of moderate or above.
- Use shade wisely
Seek shade when UV rays are the most intense, but keep in mind that shade structures such as trees, umbrellas or canopies do not offer complete sun protection. Remember the shadow rule: “Watch your shadow – Short shadow, seek shade!”
- Wear protective clothing
A hat with a wide brim offers good sun protection for your eyes, ears, face, and the back or your neck. Sunglasses that provide 99 to 100 percent UV-A and UV-B protection will greatly reduce eye damage from sun exposure. Tightly woven, loose fitting clothes will provide additional protection from the sun.
- Use sunscreen
Apply a broad-spectrum sunscreen of SPF 15+ liberally and re-apply every two hours, or after working, swimming, playing or exercising outdoors. Sunscreen should never be used to prolong the duration of sun exposure.
- Avoid sunlamps and tanning parlours
Sunbeds damage the skin and unprotected eyes and are best avoided entirely.
Sun protection programmes are urgently needed to raise awareness of the health hazards of UV radiation, and to achieve changes in lifestyle that will arrest the trend towards more and more skin cancers.
Children are in a dynamic state of growth and are more susceptible to environmental threats than adults as:
- their skin is more fragile and more reactive to the aggressions of the sun,
- sun exposure during childhood and adolescence appears to set the stage for the development of both melanoma and non-melanoma skin cancers in later life,
- a significant part of a person’s lifetime exposure occurs before age 18 and,
- children have more time to develop diseases with long latency, more years of life to be lost and more suffering to be endured as a result of impaired health.
How it works?
Sunscreens are a very effective way of protecting yourself against harmful effects from the sun. However, they should be used in combination with other methods such as sun avoidance and clothing. Remember that the aim of applying sunscreen is not to prolong your stay in the sun, but to protect the exposed parts of your body that are most at risk of getting damaged when you are out in the sun.
Sunscreens may contain physical or chemical barriers against the sun’s rays. While physical barriers reflect or scatter the UV rays, chemical barriers act by absorbing the UV radiation before it hits the skin.
Today’s sunscreens filter UV radiation in the UVA and the UVB range. The common SPF label on the tube stands for sun protection factor, a measure of how much UVB the sunscreen can block. The numbers range from 2 upwards. Unfortunately, to date there is no international standard to label the degree of protection from UVA.
Always use a sunscreen that blocks out both UVA and UVB and has an SPF of 15 or higher. To achieve good protection: Apply the sunscreen thickly and evenly to all exposed parts of your body 15 minutes before going outside. Pay particular attention to the most exposed parts such as ears, nose, forehead and neck. You should re-apply the sunscreen every two hours, especially after swimming or other sporting activities. The use of a lip balm containing a sunscreen protects against recurrent lip eruptions of cold sores.
A number of studies have shown that the vast majority of people do not apply sufficient amounts of sunscreen and therefore do not achieve the specified SPF. Approximately 35 ml of sunscreen must be applied to the total body surface of an adult to result in the SPF quoted on the tube. Hence as a rough guideline, one tube of sunscreen should last for approximately three whole-body applications. It is better to apply too much sunscreen than too little.
Sunscreens are not to be confused with after-sun creams. After-sun lotions moisturize or soothe dry and sunburnt skin, but they neither protect against the sun’s UV rays nor repair UV damage.