Crèmes anti-solaires (écrans solaires)

Dr Christophe Hsu – dermatologist. Geneva, Switzerland

What are sunscreens used for?

Excessive exposure to the ultraviolet, visible and infra-red radiation of the sun can cause sunburn, premature aging and wrinkling, brown pigmentation, hypersensitivity reactions to sunlight and skin cancer. Although your skin has its own natural defence mechanism, it’s not enough to prevent the damage caused by the ultraviolet radiation.

The so-called healthy tan is actually a response to sun damage. The skin starts to become darker and the outer layers become thicker in an effort to provide a better barrier against the sun’s rays. However, the harmful rays are still able to penetrate this natural barrier. Additional protection is essential to prevent damage into the deeper

layers of your skin.

Sunscreens are creams, lotions or oils that protect the skin from the damaging effects of ultraviolet radiation of the sun by providing a chemical or physical barrier to sunlight.

How do they work?

Chemical sunscreens absorb ultraviolet radiation, ensuring that ultraviolet light reaches only the superficial layers of the skin. Examples of some common active ingredients are PABA (paraminobenzoic acid), oxybenzone, cinnamates, and butyl methoxydibenzoyl methane.

Physical sunscreens reflect and scatter light, thus preventing the ultraviolet radiation from penetrating the skin. Examples of some common active ingredients include zinc oxide and titanium dioxide.

What does SPF mean?

SPF (Sun Protection Factor) is an index to indicate the degree of protection from sunburning that can be expected from the product. The higher the SPF, the longer the duration of the protection. Choosing the best protection. People with fair skin should start with a sunscreen with an SPF of at 15+. Those with darker skin may use a sunscreen with an SPF 6 to 8. As the skin tans, a lower SPF may be adequate.

Skin sensitivity can differ from one part of the body to another. These areas usually burn easily: nose, lips, face, ears and shoulders. The intensity of the sun varies with the seasons, time of day and location. The type of protection (SPF) required would then vary accordingly. You should however, combine the use of a sunscreen with primary protection means such as:

• Avoiding the sun when it is strongest between 10am to 4pm
• Wearing protective clothes under the hot sun. Remember that the sun rays can be reflected off the sand and cause a burn even if you are under the shade on the beach.

SKIN TYPES & SPF RECOMMENDED

Making the most of your sunscreen

• Dry your skin well before applying the sunscreen.
• Apply the sunscreen at least half an hour before going into the sun to allow for penetration and binding to the skin. * Apply the sunscreen liberally and evenly over the exposed areas of the whole body.
• Wait for the sunscreen to dry before putting on your clothes or make up.
• Re-apply every two hours, or every hour if you have been swimming with a water resistant sunscreen.
• With a non-water resistant sunscreen, re-apply after swimming or after heavy perspiration but make sure your skin is dry first.
• Do not stay out in the sun any longer than your skin and the sunscreen SPF will allow.
• Use the sunscreen even on cloudy or overcast days. The sun’s rays are as damaging to your skin on hazy days as they are on sunny days.
• Use sunscreen with SPF of 15 or higher during high altitude activities such as skiing and mountain climbing. At high altitudes, there is less atmosphere to absorb the sun’s rays, so the risk of burning is greater.

Precautions

Sunscreens only form a barrier to the passage of ultraviolet radiation. They do not make the skin more resistant to sunlight. A sunscreen must be applied frequently to maintain protection. Sunscreens can irritate the skin and eyes. Some may cause an allergic rash. If you have oily or acne-prone skin, you should avoid greasy formulations of sunscreens. When in doubt, consult your doctor or pharmacist.

Contributors:

Dr Christophe HSU – dermatologist. Geneva, Switzerland

National Skin Centre. Singapore