When we go to buy sun protection, we usually look mainly at the number of the protection factor. However, more parameters must be taken into account and for this it is essential to know what this number means in order to choose the right product and thus better protect ourselves.
Photoprotectors contain filters capable of absorbing or reflecting solar radiation, protecting the skin from its damaging effects. Of course, there are different types of radiation: ultraviolet B (UVB), ultraviolet A (UVA) and infrared (IR). That is why the protective efficacy varies against them.
Most of the products that are on the market refer to UVB rays. The Sun Protection Factor (SPF) or Protection Index (IP) indicates the number of times that the sunscreen increases the natural defense capacity of the skin against erythema or redness prior to the burn.
Although the cosmetic industry uses different methodologies to determine the SPF, the most used in Europe is the 'COLIPA'. To calculate the SPF, the minimum dose of ultraviolet radiation that produces the first erythematic reaction (or redness) perceptible on human skin, minimum erythematic dose (MED), is assessed. The MED is determined with and without protection. The relationship between the two is the FPS.
The COLIPA method classifies protection as low (2-4-6 FSP), medium (8-10-12 FSP), high (15-20-25 FSP), very high (30-40-50 FSP) and ultra ( 50 FSP). In the Health guide they warn that the data obtained and that appear on the labels do not take into account other factors such as perspiration, incorrect application of the product, the intensity of radiation and the place of exposure to the sun.
Although there is no absolute rule for choosing an appropriate protection index, the following aspects must be taken into account, according to a guide from the Ministry of Health, together with the General Council of Official Colleges of Pharmacists and the Spanish Association against Cancer. For the first exposure, never use an SPF lower than 15.
In addition, the FPS must be increased in fair skin, especially phototypes I and II. The phototype is determined by the characteristics of the pigmentation of the skin, eyes, hair, and the ability to acquire a tan.
We must also increase the protection in children, in water and mountain sports, in pregnant women or other risk groups against the sun; especially on days of high solar intensity or prolonged exposure times.
Health points out that the term "total screen" or "sun block" has been used to indicate an FPS greater than 20, and protection against other radiation. However, in reality it is misleading "since it does not guarantee full protection against radiation".
To choose a photoprotector you have to take into account a number of factors. For example, who is it addressed to, if children or adults. Another point that must be considered is the phototype of the person. The sensitivity of people to ultraviolet radiation and the formation of solar erythema (redness) depend on it. As there are different phototypes, we are not the same in front of the sun.
There are up to six types of phototypes and they are marked with Roman numerals (I, II, III, etc.). The higher the number, the darker the skin tone, eyes, and hair, and the greater the tanning ability. That is why a person with a very low phototype (I) practically does not tan and rather reddens their skin. A very clear example is that in Spain blonde tourists who have been burned are called 'prawns'.
