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With the arrival of summer, hot days lure us to enjoy the outdoors. As always, myths about sun cream are making the rounds.
Does a higher sun protection factor (SPF) offer better protection? Can a vegan diet safeguard your skin? Does reapplying sun cream extend its effectiveness? This fact check reveals the truth.
Germany’s Office for Radiation Protection recommends applying sun cream 20 to 30 minutes before sun exposure. To maintain its protective effect, regular reapplication is crucial: “At least every two hours and especially after swimming and drying off.”
However, dermatologist Christoph Liebich from Munich clarifies that there’s still a limit to how much sun you can take, no matter how much you reapply.

“For instance, if you use a sunscreen with SPF 10 and have a natural protection time of 10 minutes, your total protection lasts 100 minutes. After that, reapplying SPF 10 or even SPF 50 won’t help,” Liebich explains.
Essentially, once your skin has absorbed enough radiation, the time in which you are protected is over. And yet, to make that time as long as possible, you do need to reapply sun cream at regular intervals.

Above all, it’s important to apply an adequate amount of sunscreen from the start. Radiation protection experts say the recommended amount is two milligrams per square centimetre of skin, equating to about four heaped tablespoons for an adult’s entire body.
For a day cream to provide effective sun protection, it must contain an ultraviolet (UV) filter. Without this, there is no sun protection, says Kerstin Effers, an environmental and health protection officer in the consumer advice centre in the German city of Düsseldorf.
The SPF should be clearly stated on the packaging. “Without this information, consumers cannot assess the level of protection,” she says. Experts recommend choosing day creams with a high SPF.
It is also crucial to use a sufficient amount of day cream, just as you would with sun cream. Dermatologist Liebich cautions that some people might not apply enough expensive creams to their faces, considering them luxury products.
“If you do not apply the recommended amount, even a high SPF won’t offer adequate protection,” explains Liebich. If you’re hesitant to use enough of the day cream, it’s better to opt for a classic sun cream.

Exposure to the sun or tanning beds subjects the skin to ultraviolet (UV) radiation, which is categorised into three types: UVA, UVB, and UVC.
UVA radiation penetrates the dermis, UVB rays affect only the epidermis, and UVC rays are blocked by the ozone layer.
Liebich explains that tanning beds provide a “base tan” that offers no real protection. The light in tanning beds is primarily composed of UVA rays, which create a quick but temporary tan, while UVB radiation is often filtered out.
“To build up protection, UVB rays are necessary, but they are prohibited in sunbeds,” says Liebich.
Pre-tanning in a solarium leads to additional radiation exposure, which is why sunbeds are banned for individuals under 18. “Any additional radiation is harmful,” Liebich emphasises.

The idea of protecting yourself from tanning with a vegan diet is appealing, but experts say it’s not sufficient.
According to the German Pharmacists’ Association, while vitamin A and beta-carotene found in healthy foods can provide some natural protection for the skin, they are not enough to prevent sunburn, especially when the UV index is high.
Beta-carotene, which is abundant in fruit and vegetables, contributes to skin protection by acting as a secondary plant pigment.
Dermatologist Liebich explains that consuming these foods can help shield the skin from sunburn to some extent. However, he adds that sun cream must always be the primary means of protection, as nutrition alone cannot provide an adequate protection factor.
Sunscreen can expire and lose its effectiveness over time, making it important not to keep it for too long. Reduced UV protection can lead to sunburn in the short term and increase the risk of skin cancer in the long term.
Manufacturers indicate the recommended duration for using sunscreen after opening with a small symbol such as “12M” (meaning 12 months), which is typically found on the packaging.
It is helpful to note the opening date on the bottle to track its shelf life. Moreover, prolonged storage can cause benzophenone, a potentially carcinogenic substance, to form in sunscreens containing octocrylene, which protects against UVB radiation.
Researchers found in a study for the American Chemical Society that benzophenone gradually develops as sunscreen ages, even in unopened packs. This underscores the importance of replacing sunscreen annually to ensure its safety and efficacy.
Like what you read? Follow SCMP Lifestyle on Facebook, Twitter and Instagram. You can also sign up for our eNewsletter here.


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Sunscreen 101s, from SPF to how much to apply and how often, to how long you can keep it

Experts recommend applying sunscreen 20 to 30 minutes before sun exposure, and reapplying at least every two hours and especially after swimming and drying off. 
Photo: Shutterstock

If you use a sunscreen with SPF 10 and have a natural protection time of 10 minutes, your total protection lasts 100 minutes. After that, reapplying SPF 10 or even SPF 50 sunscreen won’t help. Photo: Shutterstock

Christoph Liebich dispels some myths surrounding tanning. Photo: Christoph Liebich

Tanning beds provide a “base tan” that offers no real protection. The light in them is primarily composed of UVA rays, which create a quick but temporary tan, while protective UVB radiation is often filtered out. Photo: Shutterstock

Beta-carotene, which is abundant in fruit and vegetables such as carrots, pumpkin, sweet potatoes and oranges, contributes to skin protection by acting as a secondary plant pigment. Photo: Shutterstock

‘Astonishing’ news on obesity and exercise: 30 minutes a week can offset heart health risk

Obese people with belly fat who do 30 minutes of vigorous exercise a week such as running have the same risk of cardiovascular disease as non-obese people, a study found. Photo: Shutterstock

Obese people who cannot manage vigorous exercise can do moderate exercise instead, such as a light jog or walk, to offset the risk of developing cardiovascular disease, but will need to do 8-9 hours a week, a study suggests. Photo: Shutterstock

Some activities, such as balance training and stretching, are light in nature, but should still be encouraged, says Professor Melody Ding, who suggests everyone should be as active as they can be. Photo: Shutterstock 

Researcher Melody Ding is a professor of public health at The University of Sydney. Photo: Melody Ding

Summer 2024 trends: 3 cooling vests and jackets tested in scorching hot Hong Kong

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South China Morning Post interns (from left) Annie Cheung, Joanne Yau and Lindsay Feng wear cooling vests and jackets in Causeway Bay, Hong Kong, on July 5, 2024. The latest summer trend, these jackets use fans, ice packs or a combination of both to keep their wearers cool. Photo: Antony Dickson

This pink polyester jacket comes with two fans that circulate cool air inside the jacket. Photo: Antony Dickson

This beige worker vest comes with four gel packs that can be frozen and placed inside the jacket. Photo: Antony Dickson

This navy cooling vest comes with up to five ice packs, while a fan helps circulate the cool air inside. Photo: Antony Dickson

This vest’s fan is operated via a power button on the left side of the chest, while the material on the outside becomes damp after prolonged use. Photo: Antony Dickson

How to prevent heatstroke in dogs, symptoms, and treatment to seek: expert summer tips

Snub-nosed dog breeds are most vulnerable to heat stroke. Photo: Shutterstock 

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A Siberian husky sits with its tongue hanging out to try to cool down on a hot day. Photo: Shutterstock

Bring plenty of water for you and your dog on a walk on a hot day – and avoid walking on cement or pavement that can burn paw pads. Photo: Shutterstock

If a dog shows any signs of heatstroke – heavy panting, bright pink gums and tongue, unwillingness to walk further – get it out of the sun and into the shade as soon as possible. Photo: Shutterstock

Choose shaded paths to walk your dog when it is hot outside. Early morning and late afternoon are safer times than midday. Photo: Shutterstock

Lifestyle

Health & Wellness

Health

Does a vegan diet protect against the sun? How many times can you reapply sun cream? A skin expert provides the facts about sun protection


Sun protection is essential to avoid radiation damaging your skin – but how best to use sunscreen, and are there other ways to protect yourself? A skin doctor debunks some myths, and offers his tips.


Skincare

Cancer

Healthy eating

Veganism and vegetarianism