It is already summer and with the new season come the questions regarding protection against solar radiation. Well, today we are going to try to clarify some questions and help you to choose which one suits you best. We cannot forget that the sun affects us all year round and that even in winter we must use creams with SPF. So, why do sun creams protect our skin?
Before delving into the subject, we must know what we want to protect ourselves from and that is specifically the ultraviolet light issued by the sun, and we will focus on two types: UVA and UVB rays, UVA radiation reaches us without being filtered by the ozone layer and is present throughout the year. It is responsible for the colour of our skin (which is nothing more – nor less – than a reaction of the skin trying to protect itself from this radiation), in turn it also causes premature aging of the skin and loss of elasticity as it slows down the synthesis of collagen.
Fortunately, UVB radiation is filtered by the atmosphere and only reaches 10 to 20% of the earth’s surface and has a higher incidence from 12:00 to 16:00 hours. These rays cause damage to DNA and as a consequence cause skin cancer. They are also responsible for erythema (burns) and hyperpigmentation.
Knowing what we are facing, we now have to decide what type of sunscreen we are going to use. There are four different types: organic, inorganic, organo-mineral, and biological, the latter is not a filter by itself, but we will explain later why we have put it here.
- 1. Inorganic filters: Also wrongly called physical filters. They are the oldest and are made by minerals, normally titanium and zinc oxide which are dispersed in the cream. They create a film on the skin that absorbs sunlight (both UVA and UVB) and then emits it with much less energy than it reaches us because these metal oxides have excitable electrons in their basal layer. Solar radiation causes these electrons to be excited and when they return to their basal state, they emit this harmless energy.
It is important to note that these filters are photostable, that is, they do not degrade with light and do not create allergic reactions. These filters have two major disadvantages: they dry out the skin and leave the typical white trace of many creams (if the particle size is reduced to 20-50 nm, better cosmetic properties are achieved). They are widely used in formulations designed for children.
- 2. Organic filters: These are the wrongly named chemical filters. These creams are created with soluble molecules based on carbon, hydrogen, and oxygen. They act by absorbing ultraviolet radiation and it is possible to carry out this absorption because they have a chromophore group that is responsible for this action, as they have aromatic groups with double bonds that have electrons capable of jumping and transforming the energy from the radiation into unnoticeable heat, which is harmless to the skin. The more incidence of the sun we have on our skin with this filter applied, it will be exhausted, and we will have to reapply it.
It is a very cosmetic product, as it is invisible, but it causes more allergic reactions than inorganic filters, as they can penetrate our skin because of their composition. They have a very wide window of protection against both UVA and UVB and are more specific, as not all that exist protect against the whole UVA range. They are the most widely used.
It is quite common to mix these two filter moles to achieve an optimal sun protection factor.
3. Organo-mineral filters: These are organic but insoluble filters, so they have the advantages of both: cosmeticity and safety. They act by absorption and by reflection and are already considered the future of total photoprotection.
4. Biological filters: They are not a protector per se, and it must be made clear that they do not replace the filters already mentioned. They are antioxidant molecules that support the skin’s immune system. They reduce oxidative stress and cellular photo-aging caused by solar radiation. The most used are vitamins A and E although vitamin C and flavonoids are also used.
These compounds can be added in creams for a topical application to enhance protection or we can also take them orally and have a reserve in our system as sun exposure exhausts the antioxidants that we have naturally in the body.
Finally, we must also know what we call the sun protection factor (SPF). It is an index that gives us the time we can remain exposed to the sun without risk of suffering burns. It is given by the quotient between the Minimum Erythemethogenic Dose (MED) of the skin with the product and without it.
SPF = MED with cream / MED without cream
In other words, a person who is able to stay 15 minutes in the sun on the first day without getting burned, an SPF 20 will give him/her 20 times more protection.
The SPF only gives us information about the protection against UVB rays. Although in Europe, protection against UVA is normally at least 1/3 of UVB.
Have you decided yet which sunscreen to use for you and yours? Leave us a comment telling us which one you stay with and do not forget to protect yourself from the sun all year round.
