The benefits and harm of solar radiation for humans have long been the subject of close attention of the world's scientists. It is known that ultraviolet rays Differ in wavelength and are divided into 3 types: UVC - short, UVB - medium length, UVA - the longest. UVC rays do not pose a hazard to humans, because Because of the short length of their waves do not reach the surface of the Earth, completely absorbed by the ozone layer of the atmosphere. Two other types differ in the degree and nature of the effect on the human skin. In addition to the benefits of sunlight, under the influence of which vitamin D is produced in the skin, which promotes the strengthening of bone tissues in the body, there is a risk of burns, premature aging of the skin and the development of melanoma (malignant tumor).
To reduce the level of harmful effects of ultraviolet sunscreens with PPD and SPF-indices are used, which serve as filters that inhibit rays, preventing them from getting on the skin. SPF filters protect against UV rays of spectrum B, PPD filters from spectrum A rays that Are most dangerous, since it is they that destroy collagen fibers in the dermis layer, accelerating the aging process, and can also lead to skin cancer. Means that contain only SPF are only able to prevent burns, and sunscreens with PPD and SPF provide comprehensive protection against sunlight types UVA and UVB. The numbers indicated on the package next to the abbreviation indicate the degree of this protection. For example, PPD cream 8 will skip over the skin 8 times less than solar UVA radiation, etc. And the number with SPF marks indicates the duration of a safe stay in the sun. When choosing a sunscreen, you need to consider your phototype, which depends on the skin color, eyes and hair. Therefore, the lighter the skin, the higher the SPF and PPD. The cream should also match the type of skin. It should be noted that the higher the degree of protection of the product, the fatter and thicker its consistency. It is suitable for dry skin type. For the most sensitive areas of the face and body with thin skin (eyelids, lips, décolletage) it is recommended to use the means with the highest protection index (30-50 units). Also, special attention should be paid to the most prominent parts of the face and body, such as the nose, ears, hips.
To sunscreens with PPD and SPF-factors provide the most effective protection, it is recommended to apply them in the same way as usual, 20-30 minutes before going out. During this time, the product will be absorbed into the skin, and it will be ready for sunbathing.
Sunscreens with PPD and SPF are applied to the skin more densely than ordinary daily caregivers. For the face, the optimal portion will be equal to the amount of cream that is placed on the finger pad, and for the body it is about two to three tablespoons.
It should be remembered that even the most resistant sunscreens lose their properties after a certain period of time and as a result of mechanical impact. Therefore, it is necessary to update the cream on the skin during the entire stay in the sun - after about two hours, and after each bath in the pond.