It is not a surprising fact that humans live in a world of duality. This is a world, where every thing has both positive and negative features, good and bad sides. Amazingly this idea is equally true not only for objects and processes, taking place on Earth, but in Space too.

Sun, a source of life on our Planet and undisputable crucial factor for maintaining existence of all living creatures on Earth, can also be harmful and dangerous for humans, animals and plants.

Even the single fact that sun is considered to be a major cause of human skin aging proves all the above said. Using medical terminology, we can say that even the sun has its side effects. To decrease the occurrence of side effects or to lower their negative impact on the organism, people invented different means and techniques.

For example, to protect eyes from harmful excessive sunlight we use sunglasses; to protect skin from negative influence of sun people use sunscreens or sun protective creams, which are to some extent sunglasses for the skin.

All the sunscreens, which are available in multiple forms, such as creams, ointments, gels, sprays etc., target ultraviolet (UV) rays. These rays are an invisible part of sunlight and there are two types of them UV-A and UV-B (there is also UV-C, but it is completely absorbed by the ozone layer, provided there is no “holes” in it:-). UV-A radiation is more harmful and dangerous for human skin, because it penetrates deeper and may cause serious problems.

When human skin is exposed to ultraviolet rays (both types), it gets damages, which can range from sunburn, rashes, and cell and tissue damage to premature wrinkling and even skin cancer.

Sunscreens usually target either UV-B rays only or both UV-B and UV-A rays. Those, which target both types of ultraviolet radiation, are called “broad spectrum” (it is usually indicated on the label). Therefore, broad-spectrum sunscreens are more preferable to use for sun protection. However, there is no mechanism of estimating protection from UV-A radiation for the time being.

Though there are many different ingredients for sunscreens, they all work similarly. In fact, all the sunscreens contain special filters with either chemical or physical nature. Their main goal is to absorb, scatter and reflect dangerous ultraviolet radiation. Physical filters are said to protect better from UV-A radiation, so carefully read the label to find the most appropriate option for sun protection among dozens of them in the store.

To make a right choice of a sunscreen, one more issue is necessary to know. “SPF” is the most vivid and for some people it is the most mysterious part of any sunscreen label. What does “SPF” mean and what does the figures after SPF mean?

SPF stands for “sun protection factor” and in combination with certain number (2, 6, 15, 25, 50) it defines how much time the sunscreen-protected person can be exposed to sunlight without getting sunburned. To determine the duration of such protection, one should multiply his usual time spent under the sun without sunburn by a number of SPF. For example, if you usually get sunburn after 20 minutes of sun exposure, then applying sunscreen with SPF 15 will ensure your sun protection for 300 minutes (in other words, with sunscreen you can spend 5 hours on the beach in comparison to only 20 minutes without the sun protection).

Of course, the calculations, described above, give average results, because the effectiveness of sunscreen depends greatly on its ingredients, types of skin and other external factors, such as swimming or heavy perspiration. To ensure the maximum results of sunscreen, it is recommended to follow the instructions on the label carefully and consult a doctor about sunscreen use in case of taking any medication.

To make the process of choosing a proper sunscreen even more easy and effective, please use the table below, which shows the interdependence between SPF and skin complexion.

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