The science of protection

Don't catch the rays : Think of UVA as rays which age, and UVB as rays which burn. Look for creams or lotions that screen out UVA besides UVB, especially in Asia where the sun is more intense.
PHOTO: The science of protection

When it comes to sun protection, the higher the SPF number the better, right? And what does the PA+ stand for anyway? L'Oreal's expert in photoprotection lays bare the facts.

So here are the definitive guidelines: You want to apply sun protection of at least SPF15 but it need not be higher than SPF50. You also want to look for creams or lotions that screen out UVA besides UVB, especially in Asia where the sun is more intense.

By now, sun protection is such a norm, especially in the tropics, it's surprising to find out that SPF standards came out only about 30 years ago. Even though the first commercial product was brought to the market in the 1930s, introduced by the founder of L'Oreal.

It's just in recent years though, that scientists are getting a better understanding of UVA just now, as opposed to just UVB. "Now, the need to be protected against UVA radiation is much clearer," says Dominique Moyal, Technico-Regulatory expert in photoprotection, L'Oreal Research & Innovation.

There are two parts to UVA, she points out, which accounts for up to 95 per cent of the solar UV radiation reaching the Earth's surface. UVA is known as the ultraviolet with a longer wavelength, but there is short UVA and long UVA.

UVB stops at 290-320 nanometres, and short UVA comes right after, between 320-340 nm. Then long UVA goes up to 400 nm - and this is the one which causes pigmentation and wrinkles.

UVA in general is less harmful in terms of cellular and DNA damage than UVB.

"But it is more damaging in terms of pigmentation and wrinkles," points out Dr Moyal.

Think of UVA as rays which age, and UVB as rays which burn.

In Asia, skin cancer such as basal carcinoma or melanoma is less frequent in the population compared to Europe or Australia. "In Asia, the percentage of skin cancer is really low probably due to the genetics of the skin but also to the different behaviour in terms of sun exposure," says Dr Moyal.

Asian skin, with its naturally high levels of melasma and phototypes 3, 4, or 5, is more sensitive to UVA however, and the consequence is pigmentation. Asians are especially prone to problems with hyperpigmentation spots, or melasma.

However, even though UVA causes wrinkles, Asians are genetically less sensitive to wrinkles, Dr Moyal notes, with wrinkles appearing later in Asians compared to Caucasians.

Wrinkle problems result from UVA penetrating more deeply into the dermis, attacking the dermis' fibres, causing wrinkles. "With UVA exposure, there is a photo oxidation of the melanin. So you have immediate darkening. After one hour in the sun, you get darkening. That's why you must protect against UVA," advises Dr Moyal, who was in Singapore recently for the launch of the La Roche Posay Anthelios XL Ultra-Light Fluid SPF50+ designed especially for the Asian tropics.

As for selecting SPFs, it's all a question of skin colour. For the Asian phototype 3, an intermediate skin colour, between SPF15 and 50+ is required, says Dr Moyal. "But even if you have darker skin, you always need to have UVA protection. An SPF30 with a UVA 15 or higher for dark skin it is the best solution," she suggests.

For "normal" skin, which means skin without problems recovering from DNA damage, then the SPF50 is maximum number you need. "SPF 100 is for people very sensitive to UVB or with a problem of DNA repair. It's not useful in Asia, because based on genetics, there is no big issue of repair to the DNA," she adds.

She says that there are very few countries having regulations allowing SPF of 100. It's 50+ in Japan, Korea and ASEAN, and 30+ in China. "Because SPF100 are for people who are very sensitive to UV light or with skin cancer, for example, when you are talking about pathology."

She adds: "It is more important to have a good balance of protection between UVA and UVB. SPF protection has both short UVA and UVB protection and globally, SPF mainly offers UVB protection." And really, SPF is related to the time you spend outside.

"If you spend only one hour in the sun, SPF 15 is enough. But if you spend more time exposed, you have to increase the factor according to the amount of time you spend in the sun," reiterates Dr Moyal. Applying it uniformly is another important practice.

Normally, when applied in a uniform layer, for about six hours, a single application of a SPF50+-PA4+ (PA++++) is sufficient. For longer exposure, re-application would be needed depending on the sun's intensity.


This article was first published on August 16, 2014.
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