Sunscreens – part one: How do sunscreens work?
The big question is of course, why should you use sunscreen. Sunscreen is good for preventing sunburn. The red color of sunburned skin is a tell-tale sign that skin cells are damaged. Damage can be induced by UVA (Ultra violet sub type A) and UVB (Ultra Violet sub type B). There is also UVC (Ultra Violet sub type C), but the ozone layer prevents UVC from entering the atmosphere. UVB increases melanin production in the skin, which makes us tan, and also causes sunburn.
UVA is perhaps even more dangerous. UVA is able to penetrate deeply into the skin, ages skin quickly and damages DNA. Damaged DNA can lead to cancer (okay, I have to admit, that the fact that ‘DNA damage causes cancer’ is a very, very brief summary about what causes cancer. Even now, scientists are still trying to figure out how and why cancer exists.)
UVA isn’t blocked by glass or the clouds. Unlike UVB, UVA doesn’t give you any warning signs. You’re not going to get a sunburn or a tan. UVA is present every day, in every season, whether it is overcast or not. My first advice would be to wear sunscreen (with at least SPF 15) every day. My second advice is to wear a broad spectrum sunscreen which protects you for both UVB and UVA. You should be able to tell from the packaging if this is the case.l
Oh, and it is wise to avoid sunbeds, according to a study in 2007, even one visit to a sunbed can increase your chances of getting skincancer (melanoma, the most dangerous kind) by 19%! (International Agency for Research on Cancer Working Group on artificial ultraviolet (UV) light and skin cancer. The association of use of sunbeds with cutaneous malignant melanoma and other skin canacers: A systematic review. Int J Cancer. 2007: 120: 1116-1122.)
How do sunscreens work?
There are two types of sun filters; chemical and physical.
Chemical filters (oxybenzone, octyl methoxycinnamate, octocrylene and avobenzone) are absorbed into the skin and absorb UV radiation. A number of chemical filters can be absorbed by the body and end up in the bloodstream. Others can generate free radicals (free radicals are bad!) when they react with the suns rays and therefore cause skin damage. This also happens if you don’t use a sunscreen!
Physical sunfilters stay on the skin and reflect the light. Good examples are titanium oxide and zinc oxide. They create a barrier to protect the skin by not allowing harmful chemicals to enter the bloodstream. They are known to not cause irritation. A drawback is that physical sunscreens leave a white film on the skin. If these sunscreens don´t leave a white film, nanotechnology is used.
What is nanotechnology?
Nanotechnology is the use of very, very tiny particles to enhance the performance of a product. The name derives from a nanometer. A nanometer is one billionth of a metre. Nanotechnology is the study of manipulating material on a molecule or atom scale. It is a relatively new study, so long term health effects are not known yet. The main concern is whether or not the particles can be absorbed by the skin and other cells of the body. This could lead to a higher dosage of the chemical in your body. The dosage of a chemical is linked to its toxicity. How higher the dosage, the more dangerous (poisonous) a chemical is. The main concern is if nanotechnology can penetrate the skin and cells. If yes, it could be dangerous, if not, we don´t have to worry. Unfortunatley, this is still being researched, so I can´t give a clear statement whether or not nanotechnology is advisable or not.
What is SPF?
SPF, sun protection factor is a (laboratory) logaritmic measure of how effective a sunfilter is. This is mentioned on the bottle. The SPF is the amount of UV radiation required to cause sunburn on skin with the sunscreen on in comparisation of the amount UV radiation required without the sunscreen.
It is said that the number of SPF determines how long one can stay in the sun without re-applying the product. For instance, if you get a sunburn from one hour of exposure to the sun, you should be able to stay in the sun for 15 hours with an SPF 15 on. This is not true. The intensity of radiation varies considerably with time of day. In early morning and late afternoon, the radiation has to pass through more of the atmosphere because the sun is nearer the horizon. The amount of SPF is determined by factors like skin type, the amount of sunscreen that is applied and the frequency of re-application, activities (sports, swimming) and the amount of sunscreen the skin has absorbed.
It is therefore recommended to re-apply sunscreen (half a teaspoon every application for the face and a shotglass for the rest of the body) every two hours and to stay out of the sun during the hottest hours of the day (12.00 – 15.00) of the day. Or go and have a nice long lunch in the shade. Or take a siesta.I mean, it’s vacation anyway.
Make up has an odd number of SPF (for instance, SPF 8 or 18) because first, the product is formulated and then the SPF is measured. Usually, an SPF in make up, or in a sunscreen in spray form isn´t as effective as a regular SPF because you have to apply the sunscreen thickly. With a spray, it is usually not easy to determine where, how thickly and evenly the sunscreen is applied. With make up it is the same way. To get the SPF that is indicated on a foundation or powder, you have to put on the foundation very thickly (a.k.a. cakey!). So it’s always better to use a sunscreen under your day cream and makeup.
SPF can’t be increased by layering it. I will explain this with an experiment. Take two glasses. Fill them with water. Add to each glass the same amount of food coloring (or dye), for instance, 3 drops. Mix well, and take half of the first glass. Put this in a new glass. Now take half of the other glass, and put it in the third glass as well. Has the color changed? No. So, if you use a daycream with SPF 15 and a foundation with SPF 15, you will not get SPF 30. It will only help you to reach the required half teaspoon of sunscreen.
As I said earlier, SPF is a logaritmic scale. This means that SPF stops 93% of the UV rays (UVA or B depending on the sunscreen). Factor 30 stops 97% of the radiation. A higher factor is not always better. The higher the SPF, the more greasy the product will feel like. If your skin type is average (meaning not extremely fair), I would recommend sticking with SPF 15 in the winter and SPF 30 in the summer.
A wee bit extra
Next to a good sunfilter, it is also wise to check the rest of the sunscreen. Are there irritating ingredients in the sunscreen, like perfume, PABA, coloring agents, methylisothiazolinone, tea tree oil, witch hazel, ylang ylang, mint or citrus? Alcohol is not good either, unless it is a fatty alcohol (just type in the name of the Alcohol in wikipedia, and scan the page on the word “fatty alcohol”. For instance, cetearyl alcohol is a fatty alcohol).
And last, but no means least, after tanning/staying in the sun and using a sunscreen, hydrate your skin! Take a luke warm shower or apply aloe vera to cool the skin. Or use after-sun.
In the next post about sunscreens, I will talk about different kinds of sunscreens, and which ones to look out for!
Until next time,