TLDR;
This article addresses common myths surrounding sunscreen use and provides evidence-based information on effective sun protection. It clarifies misconceptions about SPF, UVA and UVB radiation, the necessity of sunscreen on cloudy days, and the effectiveness of shade. It also discusses mineral sunscreens, vitamin D deficiency, activation times for sunscreens, the need for sun protection for all skin tones, and the reasons behind rising skin cancer rates.
- SPF indicates the percentage of UV radiation blocked, not the duration of sun exposure.
- Both UVA and UVB radiation contribute to skin ageing and cancer.
- Sunscreen is effective immediately upon application, not after 20 minutes.
- People with darker skin tones also need sun protection.
- Sunscreen use is not causing the rise in skin cancer rates.
No, SPF 50 Does Not Mean You Can Be in the Sun for 50 Times Longer Than If You Weren't Wearing Sunscreen
The SPF rating indicates the level of protection against UV radiation, but it's not a direct measure of how much longer you can stay in the sun without burning. SPF is a ratio comparing the amount of UV radiation needed to cause sunburn with and without sunscreen. For example, SPF 25 blocks 96% of UV radiation, while SPF 50 blocks 98%. Sunscreen should be reapplied regularly, and it's important to choose sunscreens with both a high SPF rating and broad-spectrum protection, indicated by the UVA star rating in the UK.
UVA Doesn't Just Cause Ageing and UVB Sunburn – They Can Both Cause Cancer
UVA and UVB radiation both contribute to skin damage, ageing, and cancer risk. UVA penetrates deeper into the skin, while UVB affects the outer layers. Both types of UV radiation trigger the release of inflammatory mediators in the skin, leading to long-term damage. Protecting against the broad UV spectrum, including UVA, is crucial, especially for conditions like melasma, where UVA can darken the skin.
Yes, You Can Get Burnt on a Cloudy Day
Cloud cover can vary in its ability to block UV radiation. Thick clouds may block up to 99% of UV radiation, but thinner or scattered clouds may have little to no effect. Some cloud formations can even increase UV radiation levels in certain areas. Therefore, it's important to use sun protection even on cloudy days.
Not All Shade Is Created Equal
The UV index is a key measure for determining the need for sun protection. When the UV index is three or higher, wearing a hat, protective clothing, and sunscreen, and seeking shade is recommended. However, not all shade is equally effective. Beach umbrellas offer limited protection, providing a sun protection factor of only about five. Denser canopies, like those of oak trees, offer better protection, but many trees provide minimal SPF. Reflected UV radiation from surfaces like glass, sand, and water should also be considered.
You May Not Need to Apply SPF Year-Round
The World Health Organization states that when the UV index is below two, the risk of UV damage is limited, and extra protection isn't needed. In the UK, this is typically from mid-October to mid-March. However, context matters, as snow cover can increase UV radiation. Additionally, the UV index can change quickly, so it's important to be prepared for sudden increases in UV exposure.
It's Untrue That Mineral Sunscreens Only Work If You Can See Them
Mineral-based sunscreens may leave a white cast, but this doesn't indicate their effectiveness. They primarily work by absorbing UV radiation, with only a small percentage being reflected or scattered. The visible white cast is not related to their ability to protect against UVA and UVB rays.
No, Regular Sunscreen Use Will Not Make You Vitamin D-Deficient
Sunscreen use is unlikely to cause vitamin D deficiency. Most people do not apply enough sunscreen to block all UV exposure, and the body can synthesise vitamin D3 with only a few minutes of sun exposure. Once the maximal level of vitamin D3 synthesis is reached, further sun exposure only increases DNA damage without increasing vitamin D stores. Research suggests that sunscreen users are no more likely to be vitamin D-deficient than non-sunscreen users.
Sunscreen Doesn't Take 20 Minutes to 'Activate'
Sunscreen is effective immediately upon application, despite labels suggesting a 15-20 minute wait. This waiting period allows the sunscreen to dry and form a consistent, protective film that is less likely to smear or wash off. Studies indicate that this film can form in as little as eight minutes, but following the manufacturer's instructions is always recommended.
It Is Untrue That People With Darker Skin Don't Need to Worry About UV Radiation
While melanin provides some natural protection, people with darker skin tones can still get sunburns and skin cancer. Sun exposure can also cause hyperpigmentation disorders like melasma. Dermatologists recommend that people of all skin tones use sun protection.
No, Sunscreen Is Not Causing Skin Cancer Rates to Go Up
Rising melanoma rates are not caused by sunscreen use. Factors such as ageing populations and increased sunbathing and tanning habits contribute to the rise. Studies show that UV exposure is a primary cause of skin cancers. Sunscreen can indirectly contribute to increased risk if it leads people to spend more time in the sun, feeling protected.