The Science of… Sunscreen

The sun is back! And that goes hand in hand with achieving that radiant summer glow. So what better time to look into the science of our skin, especially when it comes to sun protection and the magic of melanin.

We often hear about UV radiation, but what exactly is it? Ultraviolet (UV) radiation is a form of electromagnetic radiation emitted by the sun. There are three main types: UVA, UVB, and UVC. UVC is mostly absorbed by the Earth's atmosphere, but UVA and UVB reach our skin. UVB is the primary cause of sunburn and plays a significant role in skin cancer, while UVA contributes to premature ageing and also increases skin cancer risk. Both can damage our DNA.

This is where melanin, the pigment that gives our skin, hair, and eyes their colour, steps in. Melanin is a natural photoprotectant. This means it absorbs UV radiation, converts it into heat, and effectively scatters it, preventing it from damaging skin cells. People with darker skin tones have more melanin and a more efficient form of it (eumelanin) compared to those with lighter skin tones. This provides a greater degree of natural protection against UV radiation, offering a lower risk of sunburn and some forms of skin cancer. This reduced impact of sun damage is also why melanin-rich skin often appears to age more slowly.

However, here’s the crucial part, more melanin does not mean complete immunity from sun damage! This is a common myth that needs debunking.

Melanin provides a natural SPF (Sun Protection Factor) of around 7-10, which isn't enough to fully protect against the sun's powerful rays, especially during peak hours or prolonged exposure. Individuals with darker skin tones can still get sunburned, develop hyperpigmentation (dark spots), and are vulnerable to skin cancers, though these may present differently and often later in life. The delay in diagnosis for skin cancers in people of colour is a serious concern, often due to this misconception.

You might have seen debates online about sunscreen safety though. The good news is that the sunscreens available in the UK are regulated and widely considered safe and effective. The active ingredients are rigorously tested and the agreement among dermatologists and cancer research organisations is that the benefits of using sunscreen far outweigh any potential risks.

There are two main types of sunscreen we could be using:

• Mineral sunscreens (containing zinc oxide and titanium dioxide) create a physical barrier on the skin that deflects UV rays.

• Chemical sunscreens absorb UV radiation and convert it into heat.

• 
  

You might be thinking, but “sunscreen leaves a white cast”. This used to be a common issue, especially with mineral sunscreens (zinc oxide and titanium dioxide). However, the beauty and science industries have come a long way! Many brands now make sunscreens specifically to be invisible on darker skin tones, or use chemical filters that absorb into the skin without leaving a residue. Both are effective.

Ultimately, the best sunscreen for you is one you'll use consistently (read daily)! Look for "broad-spectrum" on the label, meaning it protects against both UVA and UVB rays, and aim for an SPF of 30 or higher.

Let us know how you’re embracing the summer safely? What are your go-to summer skincare tips? Share them in the comments!

---

Sources:

American Academy of Dermatology Association (2025). Finding skin cancer in darker skin tones. Available at: https://www.aad.org/public/diseases/skin-cancer/find/skin-of-color

British Association of Dermatologists. (n.d.). Sunscreen Fact Sheet. Retrieved from https://www.skinhealthinfo.org.uk/sunscreen-fact-sheet/

Gasparro, F.P., Mitchnick, M. and J. Frank Nash (1998). A Review of Sunscreen Safety and Efficacy. Photochemistry and Photobiology, 68(3), pp.243–243. doi:https://doi.org/10.1562/0031-8655(1998)068%3C0243:arossa%3E2.3.co;2.

NHS (2022). Sunscreen and sun safety. nhs.uk. Available at: https://www.nhs.uk/live-well/seasonal-health/sunscreen-and-sun-safety/.

Find your science tribe.

Sign up to the Lit Lab London Science and Sip mailing list for the weekly blog series, 'the Science of…', Science and Sip events and experiments to try at home!

Related posts