How to choose a sunscreen: SPF, UV filters and health

I love sun. Living in a country with six months of almost complete darkness and only few weeks of rather chilly summer makes me run outside as soon as I see the sun. But we all know that the sun produces UV light that can be harmful to our health. We are also reminded that a sunscreen is a must have in summer time. Last year, when I went to buy one, I spent nearly an hour trying to find the right product. The shops are crowded with so many different brands of sunscreens - which one to choose? Confused by such an enormous selection of products, I decided to investigate this matter properly.

After reading a dozen of scientific articles, I would like to share with you my conclusions on how to choose a sunscreen. In this post I won’t be talking about specific brands, but instead I will go through the chemical ingredients of sunscreens and explain which ones are better for you.

Why do you need a sunscreen:

  1. UV light is the main cause of skin cancer and it also contributes to other types of cancer (1).
  2. UV light is responsible for skin aging (2).
  3. UV light causes sunburns.
  4. UV light causes serious eye diseases - cataracts and macular degeneration (3).

    UV radiation is especially dangerous for children and teenagers (4)

 
UV radiation is made of UVA (95% of total UV light) and UVB rays (2). Sunburns are mainly caused by UVB light, while UVA is responsible for skin aging. Both types of UV radiation can cause cancer (5).

A typical sunscreen contains a bunch of ingredients, similar to any cream or lotion (water, oils, emulsifiers, preservatives, etc). But what makes a sunscreen different from other cosmetic products is a presence of active substances (UV filters) that interact with UV rays and prevent UV light from damaging your cells.

Depending on the nature of the UV filter present, there are three types of sunscreens:

1. Mineral (inorganic) sunscreens

Contain inorganic/mineral UV filters
Name of UV filters: Zinc oxide, titanium dioxide
How do they work: Mineral UV filters reflect UV light, preventing UV rays to pass though the skin and damage the living cells (6).
Pros:
- Efficient against both UVA and UVB radiation (2).
- More stable than synthetic sunscreens (5)
- Do not cause allergic reactions – suitable for kids and people with sensitive skin (7)
Cons:
- Have strong white color, and can be visible on the skin
- Might leave white stains on your clothes
- Often have heavy consistency and are difficult to spread

Over the last years, the consistency of mineral sunscreens has improved a lot, as it became possible to make particles of zinc oxide or titanium dioxide very small. These “nanoparticles” make the product more transparent and light and ensure better protection against UV light (8). There were some concerns about the potential toxicity of these "nano-UV filters". However, most studies showed that the nanoparticles stay mostly on the surface of the skin and cannot damage the living cells or enter the blood circulation (9, 10). Nevertheless, more studies are needed to confirm that these nano-UV-filters are safe for us and the environment.

2. Synthetic (organic) sunscreens

"Organic" here only means the chemical nature of UV filters and has nothing to do with eco-sustainability! To avoid any confusion, I will use the word “synthetic”.

Contain synthetic UV filters
Name of UV filters: dibenzoylmethane derivatives, para-aminobenzoic acid (PABA), avobenzone, octocrylene, benzophenone compounds, organic camphor derivatives, octyl-methoxycinnamate, triazone and salicylate compounds.
How do they work: Synthetic UV filters absorb UV rays.
Pros:
- Light consistency
- Active against both UVA and UVB rays if a combination of UV filters is used
Cons:
- Often cause allergic reactions (7, 11)
- UV filters can gradually degrade under UV light that, of course, decreases the protection effect of the product (12). In addition, decomposed organic UV filters can themselves become toxic.
- Danger for the environment
Every year tonnes of sunscreens end up in the sea. Many synthetic UV filters are found to be toxic to coral reefs, algae and fish (13).
- Are potentially toxic (14)

I just give few examples:
- Para-aminobenzoic acid (PABA) was shown to cause DNA damage under UV light (15). By the way, this chemical has been banned in European Union since 2008 (16).
- Some synthetic UV filters (e.g octocrylene, oxybenzone) form toxic compounds (reactive oxygen species) under UV rays (14). Octyl methoxycinnamate produces reactive oxygen species even without UV light.
- Most of synthetic UV filters have small size and can pass through the skin and reach blood circulation. For example, benzophenone-3 was even found in mother’s milk (17). It means that these chemicals can potentially affect other tissues and organs. Some studies showed that benzophenone and camphor derivatives have weak oestrogenic activity, in other words, they might stimulate cell division that can lead to cancer (18).

Fortunately, there are few exceptions: for example, triazone and benzotriasoles rarely cause allergic reactions and cannot penetrate the skin. In addition, they are very stable and can protect against both UVA and UVB rays (19).

3. Mixed sunscreens

Contain both mineral and synthetic UV filters and protect against both UVA and UVB rays. They have better cosmetic appearance, comparing to mineral sunscreens, however, they might still cause allergies.

And few words about SPF..

SPF, or sun protection factor determines how effectively a sunscreen protects you from sunburns.

What SPF to choose?

According to Food and Drug Administration, SPF of 30 is sufficient (5). But I would like to point out that the real SPF depends on many individual factors. While one might use a half of the package in one day, another will spread over just few drops of the product. In addition, sweating and swimming will also lower the labeled SPF. Therefore, I recommend to always choose a sunscreen with higher SPF to ensure a higher protection. However, even if you use a sunscreen with high SPF it does not mean that you can stay in the sun as long as you want. The longer you are in the sun, the more vulnerable you become to the long-term damage of UV light, such as skin aging and cancer.

5 Tips on how to choose a sunscreen:

I know that finding long names of chemicals on the ingredients list of each product can be annoying. But here is a tip how to determine the type of sunscreen: if you can’t find “zinc oxide” or “titanium dioxide” in the ingredient’s list, this is a synthetic sunscreen.

1. Choose the sunscreen which protects against both UVA and UVB (it is written on the package). I would recommend to use either mineral sunscreens (with zinc oxide or titanium dioxide) or sunscreens with triazone compounds.

2. Mineral sunscreens that do not contain nanoparticles are the safest choice for you and the environment. But you need to sacrifice the cosmetic appearance of the product and get used to the consistency. If you are fine with that, look for the label “nanoparticles free”.

3. In general, the higher SPF – the better.

4. Choose mineral sunscreens for your kids. If you have sensitive skin also use mineral sunscreens.

5. Look for sunscreens with antioxidants – e.g. aloe vera extract, vitamins C and E, coenzyme Q10, green tea extracts, lichen extracts (need to look through the ingredients list again) (5, 20). Antioxidants will help to protect you against skin aging and cancer.

Even if you use sunscreen regularly, don’t forget about extra measures to protect yourself from UV light. Read more about safe suntanning in my new post (coming soon!).

References:

  1. Narayanan DL et al. Ultraviolet radiation and skin cancer. Int. J. Dermatol. 49, 978–986 (2010)

  2. Stiefel C, Schwack W. Photoprotection in changing times - UV filter efficacy and safety, sensitization processes and regulatory aspects. Int J Cosmet Sci.Feb;37(1):2-30. doi: 10.1111/ics.12165. (2015)

  3. Roberts JE. Ultraviolet radiation as a risk factor for cataract and macular degeneration. Eye Contact Lens 37, 246–249 (2011).

  4. Balk SJ. Ultraviolet radiation: a hazard to children and adolescents. Pediatrics 127, 791–817 (2011).

  5. Maier T, Korting HC. Skin Pharmacol Physiol. Nov-Dec;18(6):253-62. Epub 2005 Aug 19. Review. (2005)

  6. Sunscreen Drug Products for Over-the-Counter Human Use, Final monograph, Federal register 64 27666, US Food and Drug Administration, Rockville, MD, (2000).

  7. Wong T, Orton D Sunscreen allergy and its investigation. Clinics Dermatol. 29, 306–310 (2011).

  8. Nohynek GJ et al. Nanotechnology, cosmetics and the skin: is there a health risk? Skin Pharmacol. Physiol. 21, 136–149 (2008).

  9. Filipe P et al. Stratum corneum is an effective barrier to TiO2 and ZnO nanoparticle percutaneous absorption. Skin Pharmacol. Physiol. 22, 266–275 (2009).

  10. Monteiro-Riviere NA et al. Safety evaluation of sunscreen formulations containing titanium dioxide and zinc oxide nanoparticles in UVB sunburned skin: an in vitro and in vivo study. Toxicol. Sci. 123, 264–280 (2011).

  11. Collaris EJ , Frank J. Photoallergic contact dermatitis caused by ultraviolet filters in different sunscreens. Int. J. Dermatol. 47, 35–37 (2008).

  12. Gaspar LR et al. Evaluation of the photostability of different UV filter combinations in a sunscreen. Int. J. Pharm. 307, 123–128 (2005).

  13. Gago-Ferrero P et al. An overview of UV-absorbing compounds (organic UV filters) in aquatic biota.Anal Bioanal Chem. 404(9):2597-610.Review (2012).

  14. Gilbert E et al. Commonly used UV filter toxicity on biological functions: review of last decade studies. Int J Cosmet Sci. Jun;35(3):208-19. Review. (2013).

  15. Inbaraj JJ et al. Photophysical and photochemical studies of 2-phenylbenzimidazole and UVB sunscreen 2-phenylbenzimidazole-5-sulfonic acid. Photochem. Photobiol. 75, 107–116 (2002).

  16. Commission Directive 2008/123/EC of 18 December 2008 amending Council Directive 76/768/EEC, concerning cosmetic products, for the purpose of adapting Annexes II and VII thereto to technical progress. Off. J. Eur. Union L 340/71 (2008).

  17. Gustavsson Gonzalez H et al. Percutaneous absorption of benzophenone-3, a common component of topical sunscreens. Clin. Exp. Dermatol. 27, 691–694 (2002).

  18. Schlumpf M et al. In vitro and in vivo estrogenicity of UV screens. Environ. Health Perspect. 109, 239–244 (2001).

  19. Shaath NA. Global developments in sun care ingredients. Cosmetics & Toiletries 121, 57 (2006).

  20. Radice M et al. Herbal extracts, lichens and biomolecules as natural photo-protection alternatives to synthetic UV filters. A systematic review. Fitoterapia. 114:144-162. (2016)

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