Sunscreens can protect against sunburn, but only if used correctly.

Sunscreens can protect against sunburn, but only if used correctly.

The UK product-testing charity Which? have launched a new report, which shows that some sunscreen brands are offering less protection than they claim to do.

The charity analysed the protection offered by 14 brands of sunscreen that claimed to provide a sun protection factor (SPF) of 15. They found that the majority of bottles provided the right amount of protection. However, three brands fell short, failing the test twice and providing SPFs of just 7, 10 and 12.5.

Clearly, it’s important that people get clear and accurate information about how much protection they are actually getting from their sunscreen. But aside from choosing the right bottle, there are many things that we can do to make sure we’re using sunscreens to their best effect.

SPF and star ratings

Ultraviolet radiation (UV) from the sun (and sunbeds) is the main cause of skin cancer. There are two types of UV radiation that concern us – UVB, which is well established as a cause of melanoma skin cancer and UVA, which has been more recently linked to the disease. Of the two types, UVB contributes more towards sunburns.

Sunscreens are labelled with a number called the Sun Protection Factor, or SPF for short. This tells us how much protection a bottle provides against UVB.

Cancer Research UK recommends choosing sunscreens with an SPF of 15 or higher. This gives best value for money as higher factors tend to be more expensive, while providing little extra protection. They can also be a bit more variable.

More recently, broad-spectrum sunscreens have come onto the market, which block out UVA rays as well as UVB. This is important because of the growing evidence that UVA can contribute to skin cancer.

In the UK, we measure UVA protection through the star rating, with bottles having anywhere from zero to five stars. The number of stars isn’t an absolute measure – it depends on the SPF too. We recommend using sunscreens with a star rating of four or five.

Applying sunscreen correctly

Even if a sunscreen’s SPF matches the number on the bottle, the main thing that affects how effective they are is how they are used. You can find more tips on using sunscreens correctly on our SunSmart website, but here are the most important ones.

Use with other protective measures. No sunscreen can provide complete protection from the sun. This means that in strong sunlight, or for long exposures, they need to be used together with other protective measures like clothing or shade.

Use generous amounts. The SPF value is calculated based on people applying 2mg of sunscreen for every square centimetre of skin. This means that people need around 35ml (a large shotglass or two tablespoonfuls) to cover their entire body. That’s if you’re wearing a swimming costume – for just your hands, arms and face, you need around two teaspoonfuls.

It is extremely important to apply enough sunscreen. Studies have shown that people often only apply about a quarter of what they should. In 2007, scientists showed that if people do this, the protection they are actually getting is never greater than SPF3, even if the bottle they’re using says SPF80. You can’t compensate for applying too thin a layer of sunscreen by increasing the SPF.

Never use sunscreen to spend longer in the sun. Studies have found that many sunscreens can give people a false sense of protection, leading them to spend more time in the sun than they would otherwise, and increasing their exposure to UV radiation. Surveys and randomised controlled trials have found that people who use higher factors spend longer in the sun and are more likely to experience sunburn.

Reapply every 2 hours or more frequently if washed, rubbed or sweated off. Even sunscreens that claim to be ‘waterproof’ should be reapplied after going in the water. We also recommend reapplying ‘once a day’ sunscreens, just in case you missed a bit.

Organic and inorganic sunscreens

From the emails we’ve received, there seems to be some confusion around the difference between organic and inorganic sunscreens.

The key point is that these words have technical meanings when it comes to sunscreens that have nothing to do with their use in describing food. A ‘organic’ sunscreen isn’t “more natural”, nor does it “contains fewer chemicals”.

‘Organic’ is a term used by chemists to describe molecules that contain carbon atoms. So sunscreens are organic if their active ingredients contain carbon-based molecules and they generally work by absorbing UV rays from the sun.

The active ingredients in “inorganic sunscreens”, such as titanium dioxide or zinc oxide, do not contain carbon atoms, and they work by reflecting UV rays.

In reality, most current brands are a mix of the two types and both types can help to prevent sunburn – they just work in different ways. As we’ve said, it’s using sunscreens correctly that will have the biggest impact on reducing the risk of skin cancer.