Do you know how to choose a sunscreen?

The last few days in the UK have left us feeling summer may have finally arrived. If the weatherman is to be believed this is set to continue.

Over the last few years, there has been an increased awareness about the dangers of catching those rays. But do you really understand your sunscreen label and know what to use? Many of us are aware of the Sun Protection Factor, or “SPF” rating on sunscreens. But did you know about the UVA star rating system? And what do these labels really mean?

What causes a sun tan?

Melanin is the dark pigment in our skin which causes its natural colour. Melanin is produced by cells in the skin known as melanocytes.  When our skin is exposed to sunlight the melanocytes produce more melanin as a way to absorb Ultra Violet (UV) radiation.  This increase in melanin makes the skin darker and causes the phenomenon we call a “sun tan”.  It is important to realise that a tan is a sign that the skin is damaged and is trying to protect itself.

Why we should be careful

Exposure to too much sunlight can cause a range of health hazards. The most serious of these is skin cancer.  Other problems include sunburn,  photosensitive rashesprickly heat and sunstroke.

It is important to get some sunshine, however, as sunlight is needed by our bodies to create Vitamin D. Vitamin D is needed for healthy bones and helps prevent rickets. For more information on Vitamin D and sunshine exposure, click here.  Being outside can also improve our mood and general well being. No one wants to sit inside all summer so it’s important to understand how to protect yourself whilst having fun in the sun.

UVA and UVB Radiation

The sun produces three different wavelengths of radiation, UVA, UVB and UVC. We only need to protect our skin from UVA and UVB radiation as UVC radiation is unable to penetrate the earth’s atmosphere.

UVA radiation can penetrate through windows and also penetrates the skin more deeply. Until recently it was thought that UVA was not responsible for any damage to the skin. However, we now know it is responsible for signs of skin ageing, (such as wrinkles and “sun spots“) as well as contributing to skin cancer.

UVB radiation is responsible for sunburn. It is also strongly linked to melanoma and basal cell carcinoma which are both types of skin cancer.

SPF and UVA Star Ratings Explained

SPF only protects us against UVB radiation, so it is useful in preventing sunburn. SPF factors range from factor 2 to factor 50+. The British Association of Dermatologists recommends using a minimum of SPF 30. One way to think about SPF is the percentage of UVB radiation that it filters out. SPF 30 filters out approximately 97% of UVB rays and SPF 50 filters out 98%.   If you have very sensitive skin or a history of skin cancer this extra percentage can make all the difference. No sunscreen can block 100% of UVB rays.

The UVA star rating systems show the percentage of UVA radiation absorbed by the sunscreen in comparison to the UVB. It can also be thought of as the ratio between UVA and UVB protection. The star rating ranges from 0-5, with 5 being the maximum protection. It is recommended to use a sunscreen with at least 4 stars.


An important thing to consider is that a low SPF sunscreen can have more UVA stars than a higher SPF sunscreen. This does not mean that the UVA protection is better, it simply means the ratio is between the UVA and UVB is about the same.  An SPF factor 30, with UVA 4* is better at protecting you from UVA radiation than an SPF factor 15 with UVA 5*.
It is important to always choose a high SPF and high UVA star rated sunscreen.

Protect Yourself

Hopefully, you now feel more confident about choosing your sunscreen and have a better understanding what all the labels mean!

Finally, here are some top tips for enjoying the sunshine safely while it lasts:

  • Choose a sunscreen with a high SPF  (NHS recommends at least 15, the British Association of Dermatologists at least 30)
  • Choose a sunscreen with UVA rating of at least 4 stars
  • Apply sunscreen 30minutes before going outside, and top up as you leave – click here to see how much and how to apply
  • Reapply frequently throughout the day
  • Reapply immediately after swimming – even if it is labelled as water resistant
  • Try to stay in the shade between 11 am and 3 pm
  • Wear protective clothing such as wide-brimmed hats and sunglasses
  • Keep young babies (under 6months) out of direct sunlight

If you are unlucky enough to get caught out, you can click here to learn what to do to treat sunburn.

Related articles: What is sunlight doing to you?

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Any opinions above are the author’s alone and may not represent those of his/her affiliations. Any comment is based on the best available evidence at the time of writing.  All data is based on externally validated studies unless expressed otherwise. Novel data is representative of the sample surveyed. An online recommendation is no substitute for seeing your own doctor and should not be taken as medical advice. Article edited for publication by Dr Hannah Arnstein

Images courtesy of pixabay

Sources and Further Reading

About hannaharnstein (13 Articles)
I am a psychiatry trainee working in the North East, but currently on maternity leave. Outside of medicine, other than writing I enjoy all things geek, baking and reading.

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