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Sunscreen: Decoding evidence from misinformation

Updated: Feb 17

Collaborators: Helia Haghoost, Martina Masina and Jennifer Byrne


In the battle against skin cancer statistics, sunscreen use is an important pillar in sun-protective behaviours. It is also one of the most controversial subjects where misinformation and myths are often perpetuated online and on social media. Skin health professionals play an important role in dispelling fears and providing education to encourage sun-safe behaviours with evidence-based information.





A sunscreen aims to prevent transmission of UVR to the deeper layers of the skin (dermis) where it can cause cellular damage resulting over time in changes and alternations to normal skin structure and function as well as skin cancer development. Studies support that sunscreen use can prevent skin cancer and the signs of photo-aging including wrinkles, pigment changes and telangiectasia.



Geisler, A. (2021). Visible light. Part II: Photoprotection against visible and ultraviolet light [image] from Journal Article.


What are sunscreens?


Sunscreens contain a combination of chemical (organic) or physical (inorganic) ingredients that on the most basic level either will absorb high-intensity UVR or reflect and refract it. To ensure a broad-spectrum coverage most sunscreens will combine both inorganic and organic ingredients.


Deciphering sunscreen labels

Below is some information on ingredients that may be used in sunscreen formulations. The TGA provides education and guidance that can be useful for skin health professionals




Chemical (Organic) Filters in Sunscreen


Chemical Filters, also known as organic sunscreens, are comprised of an aromatic compound attached to a carbonyl group. This structure facilitates the absorption of high-energy UV rays, exciting the molecules. After returning to the ground state, the released energy is of a low magnitude and a longer and safer wavelength in the form of heat. These filters can come in both UVA and UVB blockers as well as broad-spectrum which can absorb the full spectrum of the UV radiation.


Chemical (Organic) Filter Ingredients

UVB Blockers

  • Aminobenzoates: The most effective UVB filter but does not protect against UVA. Para-aminobenzoic acid (PABA) is associated with photoallergen or contact allergen responses, hence their usage in chemical sunscreen has declined.

  • Cinnamates: come in the form of octinoxate (OMC) and cinoxate and are UVB filters. As they are not the most potent UVB absorbers, they are combined with other UVB protectors to increase their SPF. Octinoxates degrade with time under direct sunlight.

  • Salicylates: are weak UVB filters and are used in higher concentrations or to increase the SPF of other UVB filters. They can also decrease the photodegradation of other UV filters.

  • Octocrylene: is associated with decreased instances of photoallergen reactions and can increase the SPF of sunscreens when combined with other UV filters.

  • Ensulizole: light, less oily and more cosmetically appealing. Only protects against UVB and is not effective against UVA.


UVA Blockers


  • Benzophenones: are mainly UVB filters, however, Oxybenzones can filter UVA as well. They are not photostable and have the highest incidence of contact dermatitis. 

  • Anthranilates: weak and rarely used UVA and UVB filter

  • Avobenzones: A broad-spectrum, very effective UVA filter, however very photo-unstable. It can be combined with other chemical and physical sunscreens to reduce its photo-degradation.

  • Ecamsule: Photostable, water resistant and low-systemic absorption.


Physical (Inorganic) Filter Ingredients


Physical filters can reflect and scatter UV light as they are deposited in the stratum corneum. The higher reflective index of the material contributes to the efficacy of the filter in photoprotection. How these filters react with UVR is also reliant on the particle size and thickness of the material.

The smaller, micronized particle sizes can be more cosmetically appealing due to a lack of white cast on the skin but can behave more like a chemical filter in absorbing and converting UV rays to heat. There is also a higher risk of systemic absorption. The Thicker coating can increase the filter’s reflective index but can be less cosmetically appealing. Photoreaction can cause most physical filters to become less effective, hence they are generally coated with dimethicone and silica for stability. 


Physical (Inorganic) Filter Ingredients


Zinc Oxide: A photostable and effective UVA filter that does not react with other UV filters. Not as Protective against UVB rays.


Titanium Oxide: Is a more effective UVB filter than Zinc oxide but less effective in protecting against UVA rays. Has a smaller particle size and higher reflective index, giving it a white appearance and being less cosmetically desirable. 


Iron Oxide: Whilst zinc and titanium oxide filters protect against UVA and UVB wavelengths, the visible light and near-infrared part of the spectrum are usually unprotected. Visible light and NIR are culpable in many pigmentary disorders and photodermatoses such as hyperpigmentation, melasma, solar urticaria, erythema and inflammation. Dark-coloured Iron Oxide filters provide protection against UVA, and UVB, as well as visible and near-infrared parts of the spectrum. Broad-spectrum sunscreen containing Iron oxide has shown improvement in melasma lesions and reduced relapses.


Nanotechnology and Sunscreens


Currently, nanotechnology is being widely used in sunscreens to enhance traditional sunscreen. Due to their small particle size and providing a larger surface area, nano sunscreens have the following advantages: they do not have a white cast, are non-greasy, can penetrate the skin and not become too thick, are not associated with irritation, are photostable and have higher efficacy and longer water resistance ability.


Potential new sunscreen technologies

The following ingredients are being studied for their potential to assist with sun protection and skin cancer prevention.

Vitamin C, vitamin E, selenium and polyphenols which are found in green tea extracts are photolyases (DNA repair enzymes) and antioxidants. These are potential agents of topical and nontopical photoprotection that are emerging. Niacinamide and Polypodium leucotomos extract which is derived from a fern native to Central and South America, are used orally as photoprotective agents. 

Exposure of cells to UV light from the sun causes the formation of pyrimidine dimers in DNA and has the potential to lead to mutation and cancer. The use of Nicotinamide has been shown to enhance DNA repair and decrease the formation of pyrimidine dimers in human keratocytes. 

When taken orally P. leucotomos extract can increase the minimal erythema dose of sun exposure without significant adverse effects. This ingredient is also helpful for dermatologic diseases induced by ultraviolet radiation, such as polymorphous light eruption and solar urticaria. 


Myth busting – Sunscreen 


  • Inorganic (physical) sunscreens are superior as they reflect UVR and do not absorb it into the skin. This is a commonly perpetuated opinion. As stated above micronised inorganic molecules have been found to behave comparably to organic compounds by absorbing UVR due to their molecular size.  To have a broad. spectrum coverage of UVR most sunscreens will combine both inorganic and organic filters. However, in some situations, sunscreens with a higher zinc oxide content may be recommended due to other benefits on the skin including reducing itch, and soothing chapped and irritated skin. 

  • You can create your natural sunscreen – Sunscreens are not easy to make and are a regulated therapeutic good in most situations to ensure that they are broad spectrum, reliable and stable during use.  A sunscreen made in your kitchen is not going to meet these requirements.    

  • SPF 30+ and SPF 50+ or higher are the same – SPF is determined by the ability of the formulation to filter out UVB radiation.   In laboratory conditions, SPF 30+ will filter out approximately 97% UVB radiation, SPF50+ 98% and SPF 100 will filter out 99%.  These tests are carried out with a 2mg/cm2 thickness.  In real use, most people don’t apply their sunscreen to this thickness and therefore are not receiving the labelled SPF.  It can be recommended to use the highest SPF rating that is available to provide the best protection possible as well as education on how much to apply to get good protection. 

  • Dark-skinned individuals do not need sunscreen – While melanin-rich skin has more natural protection for UVR, all skin types can experience photodamage and skin cancer, particularly melanoma.  Research indicates that darker skin types may have a delayed diagnosis of skin cancer compared to lighter skin types due to the higher pigment content in their skin.  Therefore, all skin types can benefit from the use of sunscreen to prevent sun damage. 

  • Sunscreen in makeup is enough sun protection – most makeup has SPF15 or lower which is below the SPF30 recommendation 

  • Staying in the shade prevents the need for sunscreen - see below

  • If I apply sunscreen that's enough to prevent skin cancer - see blow

  • Sunscreen is not required if I am not in direct sunlight, working indoors or it's cloudy - see below Light can be reflected, scattered, and transmitted therefore we need to use multiple sun protection strategies to effectively protect against sun damage.  Using any one method alone will not be as effective as using all five (5) slip (on protective clothing), slop (on sunscreen when UV Index is above 3), slap (on a hat), slide (on your sunglasses) and seek shade, particularly in peak UV periods 

  • Sunscreen is not safe – see facts about sunscreen 

  • Sunscreen prevents Vitamin D synthesis – see facts about sunscreen 


Facts about sunscreen 

 

  • The best sunscreen is one that has evidence-based efficacy and safety, and that you can access, afford, and use regularly. 

  • Sunlight is required for Vitamin D synthesis however it has been found that 10-15 mins on the face, arms or legs early in the morning when UV is at its lowest for the day may be enough to offset this in Australia.  Due to the strong evidence to support sunscreen in the prevention of sun damage and skin cancer development, you may seek expert medical advice about whether Vitamin D supplementation is suited to your situation rather than not wearing sunscreen at all or risking overexposure of your skin to UVR by sitting out in the sun to get your Vitamin D.

  • Visible light and Near Infra-Red is also attributed with photo-damage and photo-aging therefore some sunscreens will incorporate filters such as iron oxide (pigment) to protect against this portion of the spectrum.  

  • Sunscreen is safe to use.  Skin reactions can occur in some people and are more common for some organic ingredients.   In most people changing their sunscreen to a different formulation can alleviate this and test patching before use is recommended.  Inorganic ingredients have not been found in studies to be systemically absorbed, and while there are studies that report systemic absorption of organic filters most studies indicate that in real-world applications people don’t apply an amount that would be needed to cause harm.  Sunscreens have been used since the 1970s and evidence generally points to the safety of sunscreens overall.  Studies that report effects as an endocrine disruptor have low-quality evidence in humans at this time.  Concerns for effects on the environment have led to some countries limiting the use of certain ingredients however coral bleaching is impacted by a variety of factors and it is still controversial as to whether this can be attributed to sunscreen use in a real-world context.  It is always important to continue research and keep up with information as further updates become available.

 

Ingredients & Regulations 


For more information, you can visit the Therapeutic Goods Administration (TGA) for detailed information on permitted ingredients, concentrations and the regulatory requirements and exemptions for sunscreen.  

 

 

Recommendations  

 

  • It is important to remember that sunscreen should be used along with other sun protection strategies including broad-brimmed hats, cover-up clothing, sunglasses and seeking shade

  • Sunscreen is not recommended in infants below 6-12 months. Babies and toddlers should be kept out of the sun and be covered with sun-protective clothing. If it must be used it is advised to be washed off as soon as possible. 

  • Children and those with more sensitive skin or barrier impairment may be recommended to use sunscreen with a higher component of physical (inorganic) ingredients however this is not always the case, personal preference, previous history and skin response are the best gauges to use.

  • Apply liberally and reapply if you are going to be sweating, in water or sunscreen may be rubbed off

  • While sunscreen may have some effectiveness as soon as it's applied it is still highly recommended to apply it at least 15 minutes before sun exposure.




Disclaimer


The information in this document is general only and is not, and is not intended to be advice. Before making any decision or taking any action, you should consult with appropriate accounting, tax, legal or other advisors. No warranty is given as to the correctness of the information contained in this publication, or of its suitability for use by you. To the fullest extent permitted by law, the Australian Society of Dermal Clinicians Inc. (ASDC) is not liable for any statement or opinion, or for any error or omission contained in this publication and disclaims all warranties with regard to the information contained in it, including, without limitation, all implied warranties of merchantability and fitness for a particular purpose. ASDC is not liable for any direct, indirect, special, or consequential losses or damages of any kind, or loss of profit, loss or corruption of data, business interruption, or indirect costs, arising out of or in connection with the use of this publication or the information contained in it, whether such loss or damage arises in contract, negligence, tort, under statute, or otherwise


References


  1. Bennett SL, Khachemoune A. Dispelling myths about sunscreen. J Dermatolog Treat. 2022 Mar;33(2):666-670. doi: 10.1080/09546634.2020.1789047. Epub 2020 Jul 7. PMID: 32633165.

  2. Chavda, V. P., Acharya, D., Hala, V., Vora, L. K., & Dawre, S. (2023). Sunscreens: A comprehensive review with the application of nanotechnology. Journal of Drug Delivery Science and Technology, 104720. https://doi.org/10.1016/j.jddst.2023.104720

  3. Gabros, S., Nessel, T. A., & Zito, P. M. (2019). Sunscreens and photoprotection. https://europepmc.org/article/nbk/nbk537164

  4. Geisler, A., Austin, E., Nguyen, J., Hamsavi, I., Jagdeo, J., & Lim, H. (2021). Visible light. Part II: Photoprotection against visible and ultraviolet light. Journal of the American Academy of Dermatology, 84(5), 1233-1244. https://doi.org/10.1016/j.jaad.2020.11.074 

  5. Pratt, H., Hassanin, K., Troughton, L. D., Czanner, G., Zheng, Y., McCormick, A. G., & Hamill, K. J. (2017). UV imaging reveals facial areas that are prone to skin cancer are disproportionately missed during sunscreen application. PLoS One, 12(10), e0185297. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0185297

  6. Rodan, K., Fields, K., Majewski, G., & Falla, T. (2016). Skincare bootcamp: the evolving role of skincare. Plastic and Reconstructive Surgery Global Open, 4(12 Suppl). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5172479/

  7. Sander, M., Sander, M., Burbidge, T., & Beecker, J. (2020). The efficacy and safety of sunscreen use for the prevention of skin cancer. Cmaj, 192(50), E1802-E1808

  8. Sarkar, R., Arora, P., & Garg, K. V. (2013). Cosmeceuticals for hyperpigmentation: what is available?. Journal of cutaneous and aesthetic surgery, 6(1), 4 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3663177/

  9. Tanaka, Y., Parker, R., & Aganahi, A. (2023). Photoprotective Ability of Colored Iron Oxides in Tinted Sunscreens against Ultraviolet, Visible Light and Near-Infrared Radiation. Optics and Photonics Journal, 13(8), 199-208. 10.4236/opj.2023.138018



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