All About Sunscreen

All about sunscreenThe summer vacation is getting closer and it is about time to stock up on sunscreen. In recent years, we have seen a lot of warnings about sunscreen being more harmful than the sun. That sunscreen in itself increases the risk for skin cancer, is toxic, hormone-disrupting and stops the important production of vitamin D that has a protective role in cancer development. All this is confusing, to say the least. How should you protect yourself from the sun? Or is it better to avoid sunscreens altogether? 


Why Protect Yourself Against the Sun?

According to the American Skin Cancer Society, 90% of all non-melanoma and 86% of melanoma skin cancer cases are related to sun and UV-light exposure [1]. Sunlight, mainly the strong UV-rays, but to some part also visible and infrared light, causes changes in the skin cell's DNA and other cellular components. Most of the DNA changes are repaired immediately but can, if you are unfortunate, because it actually comes down to chance, transform a cell into a cancerous one. Simply put, this transformation leads to cells dividing without control or consideration for its neighbors and can, with time spread (metastasize) and destroy the body's inner organs.

Both UVA och UVB can cause skin cancer. Most dangerous are the shortwave UVB-rays. They can directly damage DNA but comprise only 5% of the UV-light that reach us through the atmosphere. The rest is UVA, which consists of longer rays that are weaker but, on the other hand, penetrates deeper into the skin layers where they cause free radical formation that in turn can damage the cell's DNA. UVA also damages other cellular components and is the foremost cause of skin aging. In addition, exposure to UV-light, both A and B, turns off the immune cells that are present in the skin, the Langerhans cells, normally are responsible for surveillance of foreign particles in the skin, like antigens from tumors and viruses [2]. That means that the skin's ability to get rid of tumors is seriously hampered after exposure to UV-light. 

An Australian study compared daily use of sunscreen containing SPF 15 over 4 years with discretionary use. When followed up 8-10 years later the result was a drastic decrease in the number of several types of skin cancer [3,4]. The same research group has later made scientific calculations over how much regular sunscreen use could affect the number of skin cancer cases in the world's fair-skinned population. Their conclusion was that if everybody started to use sunscreen daily, the number of skin cancer cases would decrease by 30-40% [5].


What Does SPF Mean and How Much Sunscreen Do You Need?

SPF is short for sun protection factor and refers to how much of the UV-light that reaches the skin. If we take SPF 15 as an example, 1/15 of the light will reach the skin, meaning that you theoretically can stay out in the sun 15 times longer before you turn red. So if it normally takes 20 minutes before you start to turn red, with SPF 15 you can stay out in the sun for 5 hours before your skin start to burn (20 min x 15 = 300 min). This under the condition though, that you have slabbed on a thick enough layer and also reapplied the cream every 2 hours. Sunscreen loses its effect with time and even if it is waterproof, friction from sand, clothes and bath towels removes it.

The problem with sunscreen is that we do not use enough and simply forget to reapply, which gives a false impression of security. To obtain the stated SPF, you need as much as the size of a golf ball of sunscreen every 2 hours to cover the whole body. Studies show that we more often than not, use much less and obtain only 1/3 of the SPF stated on the bottle [3]. What is even more worrisome is that tests on sunscreen have shown that several brands of sunscreen exaggerate the SPF in their products.

SPF 15 is considered the lowest level to achieve an acceptable protection from the sun to minimize the risk of skin cancer. If you want to protect your skin against sun-aging a much higher SPF is required, at least 30 but rather 50 or 50+. Also, remember to get a sunscreen that protects against UVA as well. The SPF refers only to UVB protection. In Europe, sunscreens that claim to protect against UVA should contain a UVA protection that corresponds to at least 1/3 of the UVB protection.


How Much Does Natural Sun-Blockers Protect

The sun is strongest the four hours around noon. Between 11:00-15:00 it is wisest to stay in the shade but how much of the UV-light is actually blocked by shade? Clouds, for example, do not stop the UV-light as much as one would think [6]. The suns heat, the infrared rays, are much more efficiently blocked by a lightly covered sky than the UV-rays, which can be misleading since we usually interpret the heat as a measure of sun strength. Certainly, the amount of UVB that reaches us decreases the thicker the clouds, but most of the UVA-rays passes freely through clouds and even windows. Neither are you particularly well protected under water. While snow reflects about 90% of the UV-light, water lets about 80-95% through, depending on how choppy it is.

The shade from a small parasol does not provide full sun protection but corresponds to an SPF of 3-10. The shadow from a tree varies between SPF 4-50 depending on the thickness of the crown and how close to the stem you are. Thin summer clothes are considered to give a sun protection of about 10. Thicker weaved fabric and darker and stronger colors increase the clothes sun protection. The advantage with clothes is that they give a constant sun protection over time.


Melanin – Our Bodies own Sun Protection

When the skin is exposed to UV-light, it produces melanin that protects the living cells in the skin from further sunlight. There are two types of melanin though, eumelanin and pheomelanin [2]. Fair-skinned and redheads have the misfortune of producing significantly less of the more effective eumelanin and instead more of pheomelanin that offers a lesser protection against the sun. By building up a tan slowly and avoid getting burnt you give the skin time to react and produce melanin. This way you enhance your natural protection against UV-light to a certain degree. But if you are really fair-skinned, you can never achieve the amount of sun protection that exists in naturally dark skin.


Eating Your Sun Protection?

Intake of certain vitamins and antioxidants have in tests shown to render the skin less sensitive to sun damage. Most interesting effects have been seen with carotenes like beta-carotene, lutein and lycopene that you find in carrots, tomatoes and watermelons, polyphenols found in green tea, red wine and dark chocolate, omega-3 fatty acids from fatty fishes and vitamin E in combination with vitamin C [7,8]. This is very exciting research but one should be aware that in order to reach the desired effect we are talking about a regular intake for up to two months and that the sun protection effect only corresponds to a couple of steps on the SPF scale, at the most. It is certainly fantastic that you can build up a greater tolerance against the sun, but it does not mean that you thereby can walk around during midday on a clear summer day and think that the sun does not reach you.


Warning for DIY Sunscreen

The dream about an all-natural sunscreen has created a hype for certain ingredients on social media and we do understand the enticement. Unfortunately, there is no scientific proof that any of these ingredients have inherent sun protection properties and when we last summer did our own test on raspberry seed oil and coconut oil we could not find that they provided any visible protective effect that came even close to SPF 10. With homemade sunscreen, even with additions of ZnO or TiO2, the final result is, at best, unreliable. It is just not possible with only home equipment to achieve the even mixture of the ingredients required for adequate sun protection. In addition, the other ingredients included in the mixture also has a huge impact on the result. Even for very experienced cosmetics formulators, it is difficult to predict the SPF that a certain mixture will have. We, like several other websites, would like to heed a warning for attempting to formulate your own sunscreen if you do not have access to advanced lab equipment and techniques to measure the achieved SPF.


How Much Sun for Vitamin D production?

The majority of our vitamin D, all of 80%, comes from a reaction in the skin that requires sunlight. In the northern hemisphere, the sun is too weak during the winter months to promote vitamin D production and we have to build up stocks during the summer months. Sunscreen severely hampers the production of vitamin D in the skin, already at SPF 8, the production is limited by 97,5%. So how much sun is actually needed then for adequate vitamin D production? That depends both on the strength of the sun and your skin's sensitivity. But if the sun is strong enough to turn your skin slightly red in half an hour, then it is enough to expose your face, arms, hands and legs to unshielded sunlight for about 6-8 minutes, 2-3 times a week to fill up your vitamin D storage [7,8]. About the same time as a short walk during the lunch break.


ZnO and TiO2 - Nano or Not Nano?

Unlike the other UV-filters that are chemical and absorb the UV-light, zinc oxide (ZnO) and och titanium dioxide (TiO2) are physical UV-filters that blocks and spreads the UV-rays. Zinc oxide was the active ingredient in the very first sunscreen products launched in the 1930s and protects against both UVA and UVB. The drawback with both zinc oxide and titanium dioxide is that they are visible and gives the skin a white cast. This is, of course, a cosmetic issue but makes a lot of people shy away from sunscreens with physical UV-filters or they use too thin a layer to avoid the white look. The white effect decreases with the decreasing particle size, without affecting the protection against UV-light. Really small particles, so-called nanoparticles are smaller than 100 nanometers, that is 0,0001 millimeters. Laboratory studies have implied that zinc oxide and titanium dioxide can cause the formation of free radicals when exposed to UV-light, which, of course, could be harmful to the cells. However, it is only harmful if the zinc oxide or titanium dioxide in the sunscreen reach down to the living cells. Numerous studies have been done on the subject and they all show the same thing - that neither zinc oxide nor titanium dioxide of nanoparticle size reach the underlying layers of the skin where there are living cells [9]. Therefore, we consider the fear of nanoparticles in sunscreen exaggerated. ZnO and TiO2, whether nano or not nano, are the safest alternatives when it comes to UV-filters. However, always avoid nanoparticles in products where there is any risk to ingest the product such as with SPF lip balms, sunscreen on spray and when it comes to small children that keep putting their fingers in the mouth. 


Mineral Powders and Sun Protection

Mineral cosmetics such as powders and foundations can provide sun protection of about SPF 15 -20. Be careful to choose mineral make-up where ZnO or TiO2 are key ingredients, that is are being named high up in the ingredients list. Remember also that as with all sunscreen products, the actual SPF depends on how much powder you use. 


What You Should Absolutely Avoid in Your Sunscreen

For some parts of the year, we put on thick layers of sunscreen several times a day. This results in a much higher uptake of the content of a sunscreen compared to an ordinary moisturizer. What is more, you expose the cream to UV-light that might cause break-down of certain ingredients, forming other harmful substances that are not listed among the ingredients. In recent years, some of the UV-filters approved to use in sunscreens have been shown to have negative side-effects such as being hormone disruptive or allergenic, etc. You can read more about which substances you definitely should avoid in sunscreen and why here...


Buying Sunscreen Abroad

It can be tempting to buy your sunscreen after you have arrived at your holiday destination instead of bringing the bottles with you on the flight. In many cases, the sunscreen might also be cheaper abroad than at home. But if you are vacationing outside of Europe, you should be aware that the regulations for what sunscreen products are allowed to contain vary considerably around the world. In the US for example, the situation regarding approval of new UV-filters is at the moment very problematic [10]. No new UV-filters have been approved by the FDA for a very long time and filters that in Europe are considered both safer and more efficient in protecting against UV-light, especially UVA-filters, are not allowed in the US. As a result, sunscreens on the American market contains older types of UV-filters that in Europe are being phased out by European producers. Tests have also shown that American brands of sunscreen that are labeled broad spectra let through 3 times as much UVA as their European counterparts. Added to the fact that you can count on your fingers the substances that in the US are not allowed in cosmetics, while the EU's corresponding list, Annex II, at the moment contains 1382 substances, we strongly recommend that you stock up on sunscreen before the sun vacation to Florida. 



Sunscreens do decrease the risk of skin cancer so remember to protect yourself against the sun. It is best to avoid being out in the sun during the four hours around noon when the sun is the strongest. It is always good to use hats, sunglasses and long-sleeved shirts but it might not always be possible as the only sun protection. Remember that neither shade nor summer clothes give complete sun protection if you spend a whole day in the sun. Sunscreen products with physical UV-filters like zinc oxide and titanium dioxide are safer than the ones containing chemical filters. But the best sunscreen is the one that you actually use. If you hesitate to put it on because you resent the smell, dislike that it gives your skin a whitish look, or makes your skin break-out, it is not the right sunscreen for you, even if it contains only good ingredients.

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  3. Green, A.C. et al., Reduced melanoma after regular sunscreen use: randomized trial follow-up. J Clin Oncol, 2011. 29(3): 257-63.
  4. van der Pols, J.C. et al., Prolonged prevention of squamous cell carcinoma of the skin by regular sunscreen use. Cancer Epidemiol Biomarkers Prev, 2006. 15(12): 2546-8.
  5. Olsen, C.M. et al., How many melanomas might be prevented if more people applied sunscreen regularly?, Br J Dermatol, 2018. 178(1): 140-147.
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  7. Holick, M.F., Sunlight and vitamin D: both good for cardiovascular health. J Gen Intern Med, 2002. 17(9): 733-5.
  8. Norval, M. and Wulf, H.C., Does chronic sunscreen use reduce vitamin D production to insufficient levels?, Br J Dermatol, 2009. 161(4): 732-6.
  9. Australian Government, Dept. of Health and Ageing, A review of the scientific literature on the safety of nanoparticulate titanium dioxide or zinc oxide in sunscreens, 2009: 1-32. Available at:
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