What does SPF hide?

For some a cosmetic routine all year round, others seemingly know about them but prefer not to apply or do it badly. Why are sunscreens still such a tricky subject? And why should we use them after all – especially in summer? Plus a short guide on how and how often to apply them.

For centuries in our culture, it was pale skin that was most desirable. Aristocratic whiteness indicated that its owner did not need to work physically, especially outdoors. They could protect themselves from the sun with gloves, a hat or an umbrella, for example. Not only did they protect themselves from the sun, they also lightened their skin with lead- and mercury-based cosmetics. In addition to accessories, various powders, ointments or drinking vinegar were supposed to help with sun protection.

The change came in the inter-war period thanks on the one hand to John Harvey Kellogg (the flake man), who advocated the health-promoting properties of sunlight, and on the other hand to women’s magazines explaining to their readers that tanned skin was healthy and pretty. Coco Chanel was also said to have contributed to the fashion for bronze, who in 1923 was said to have caused a scandal by arriving tanned at an elegant party. Anyway – again, one had to stand out. Since the working class now had pale skins as a result of working long hours in factories, the upper class had to have a darker shade.

Today, a tan is still in demand and shows that a holiday was successful. At the same time, there is an increase in people who do not tan at all or only want to be sun-kissed, an effect they achieve with high SPF filters.

In the ultraviolet

Our bodies need the sun to produce vitamin D. It helps to absorb calcium and phosphate, so it is essential for our bones, teeth and muscles. Its deficiency causes rickets in children, for example. On the other hand, the sun burns the skin and accelerates the process of photo-aging (i.e. sagging and loss of firmness). It also contributes to the development of skin cancer. But one step at a time.

Sunlight has three ranges: ultraviolet, visible light and infrared. We are interested in ultraviolet – yes, it’s that UV abbreviation on the sun cream packaging. We have UVA, which is ultraviolet with a wavelength range of 315 to 400 nm, UVB – here the wavelength range is 280 to 315 nm, and UVC (100 to 280 nm), which is trapped by the atmosphere.

UVB radiation, which stimulates the synthesis of melanin, is responsible for the browning of our skin, but can cause burns. It reaches the stratum corneum layer of the skin. There it stops, although a small part can reach the dermis. UVB damages collagen fibres (which contribute to the formation of wrinkles) and also the Lagerhans cells in the epidermis, which are co-responsible for the functioning of our immune system. Very little of this radiation reaches the earth – just 5 per cent of all UV rays. We are most affected by them in summer, especially in the forenoon.

95 per cent of the rays belong to UVA, which is far more insidious than UVB. First of all, it reaches us all year round, whatever the weather, penetrates clouds, glass and clothing, and its intensity does not change during the day. It penetrates deeper – all the way down to the dermis. We see its effects later than UVB. And they are remarkable, because UVA is responsible for the formation of free radicals that damage cells. It is also what causes freckles and pigmentation changes to appear on the skin. It also contributes to the formation of skin cancer.

That’s why it’s important to protect ourselves from the sun at all times. And our best shield will be sunscreens. However, it is important to stress that no sunscreen will give us 100% protection.

20, 30 or 50?

SPF, or Sun Protection Factor, is the factor that determines the degree of protection against UVB radiation. You will find cosmetics with different SPF values – not only those for sunbathing, but also some face creams and lipsticks.

What is the difference between a cream with an SPF of 6 and one with 50? Every skin has a certain time of exposure to the sun, after which an erythema develops. This time depends on the phototype and, for people born in our geographical latitude, is not long, usually a few minutes. The SPF value tells us how many times longer we can safely be in the sun. Thus, if we assume that without sunscreen, erythema appears after just 5 minutes, SPF 6 extends this time to 30 minutes and SPF 50 to more than three hours (250 minutes). Of course, this is provided that we apply the amount of cream recommended by the manufacturer (more on this below).

So, creams with SPF 6 and 10 will give us low protection, medium protection will give us SPF 15, 20 and 25. If we need high protection, let us choose SPF 30 or 50. Very high protection will be given by a cosmetic with SPF 50+.

What about the others?

SPF is the most well-known factor, but – as we mentioned – it only protects against one range of radiation. You will also find other designations on sunscreen packaging – UVA in a circle, PA with a different number of pluses, IR or HEV. And immediately the issue gets complicated.

Let’s start with UVA. If UVA is in a circle on the label of a cream, it means that the UVA protection is at least one-third of the UVB protection (i.e. SPF).

PA with pluses provides us with more precise information. It uses PPD (Persistant Pigment Darkening), a factor very similar to SPF, except that instead of erythema we have pigmentation. The PPD tells us how much the UVA dose will be reduced if we apply a filter. The PA+ scale is used to express this. Thus, if the PPD is 2-4, the protection is PA+, PPD 4-8 is PA++, PPD 8-16 is PA+++ and PPD above 16 is PA++++. And it is the four pluses that will give us the best protection.

In the UK and Ireland, on the other hand, the Boot’s scale, which determines the ratio of UVA to UVB protection, is popular. The higher it is, the more stars. The maximum is five and this means that the UVA-protective filter has more than 90 per cent of the value of the UVB filter.

On some cosmetics we can find two other designations. IR is the infrared filter and HEV the visible light filter.

It is worth mentioning that in the European Union it is only mandatory to indicate the SPF value. Information on the degree of UVA protection is not necessary, although the EU recommends that UVA protection should be one third of the UVB protection.

Chemical or mineral?

Sunscreens are divided into chemical, mineral (physical) and mixed.

Chemical ones penetrate our skin (which is why they should be applied 30 minutes before going out in the sun) and absorb UV radiation, turning it into heat energy. They are lightweight and absorb easily, leaving no film on the skin. They are therefore resistant to abrasion, but are not particularly photostable – this means that the sun and temperature limit their durability. They therefore need to be reapplied after 2-3 hours. In the cosmetic composition you will find them under the names: Octorylene (note, this is better not to take to the seaside – we wrote about it here), Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (Tinosorb M, Bisoctrizole), Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (Tinosorb S, Bemotrizinol), Diethylamino Hydroxybenzoyl Hexyl Benzoate (Uvinul A Plus), Disodium Phenyl Dibenzimidazole Tetrasulfonate (Neo Heliopan AP, Bisimidazylate), Terephthalylidene Dicamphor Sulfonic Acid (Mexoryl SX, Ecamsule), Drometrizole Trisiloxane (Mexoryl XL, Examsule), Ethylhexyl Triazone (Uvinul T 150), Diethylhexyl Butamido Triazone (Uvasorb HEB).