SOLAR FILTERS: WHAT ARE THEY AND HOW DO THEY WORK?

THE sun filters they are substances, natural or synthetic, that are included in cosmetic formulations to protect them from damage caused by solar radiation . In the case of sun cosmetics, they are responsible for the “protection factor” or SPF ( Solar Protection Factor ), the value of which indicates how much the sunscreen product will protect from the sun our skin, avoiding rashes and other damage such as photo-aging.

What are sunscreens and how do they work?

The principle is very simple: Sunscreens reduce the amount of light radiation which affects the surface on which they are applied, for example on the skin. The difference between the different types of filters lies in as achieve this result.

THE physical filters they reflect a portion of solar radiation , allowing only a limited amount to pass through the skin. They, therefore, do not interact with solar radiation and are not altered in any way.

THE chemical filters , on the contrary, they absorb part of the radiation solar and use it to reach higher energy quantum states. This immediately excess energy is released in the form of heat, so that the filter is ready to absorb more solar radiation.
The different mechanisms of action are summarized in the figure alongside. In both cases, the amount of energy which is let through (i.e. which is not reflected or absorbed) depends on amount of filter applied , which determines the protection factor.Each of the two types of filters offers advantages and disadvantages : i physical filters they have the advantage of being completely stable and not being damaged by solar radiation. Also, compounds such as zinc oxide they are totally inert therefore they are very safe for the skin. Their disadvantage is the difficulty in achieving high protection without producing the white effect . To reduce this effect it is possible to use them in a micronized form, which is much more valuable (BeC uses them in all sunscreens) . But even in micronized form it is not possible to achieve very high protections without them becoming visible.

Therefore, in high protections they are associated with chemical filters . Chemical filters have the advantage of being very effective and offer high protections as well being invisible , they disperse better in the formulation giving a more homogeneous protection (which corresponds to a more homogeneous tan!), but since they absorb the energy of solar radiation, they have the risk of photo-degradation or to give rise to photochemical reactions.

In conclusion, let's clarify an important point: often the expression chemical filter is confused with synthetic filter that is, artificial, while it is believed that the physical filter is natural. This is not necessarily true!
Physical filters are normally inorganic, i.e. mineral salts and are usually natural, but they can also be synthetic, i.e. artificially produced.

On the contrary, the most common chemical filters are often synthetic, i.e. man-made, however there are also some examples of natural chemical filters. One of the most important is the gamma-oryzanol which is extracted from rice bran (see figure alongside), but there are others such as cinnamic acid , contained in cinnamon, widespread in Brassicaceae plants (cabbage, broccoli) and in Shea butter, carotenoids (contained for example in carrots, tomatoes and a variety of red-orange fruits), the Vitamin E and numerous others.

These compounds also have the advantage of having additional properties (e.g. antioxidant, soothing, anti-reddening, anti-aging, etc.), unfortunately, however, they do not have the same effectiveness as synthetic chemical filters. BeC uses natural chemical filters when high protection factors are not necessary (e.g. Huile SolE'), but when these are necessary, synthetic ones must also be associated. Therefore, let us not be fooled by the words such as chemical or physical filters referring to the mechanism of action and not their origin . This can be natural or synthetic, but the really important thing is the their stability to solar radiation which is essential for our safety in the sun.