Sunscreen myths, debunked: The truth on re-applying and 'pre-tanning'

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.

Re-applying prolongs sun protection:

True, but only to a degree

Germany's Office for Radiation Protection (BfS) 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 re-apply.

"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 re-apply 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.

A day cream is sufficient as light sun protection:

True in some cases

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, environmental and health protection officer.

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's 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 don't 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.

'Pre-tanning' in a solarium protects the skin:

False

Exposure to the sun or tanning beds subjects the skin to ultraviolet (UV) radiation, which is categorized 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 emphasizes.

A vegan diet protects against sunburn:

True

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 (Abda), 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 fruits 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.

Sun cream can expire:

True

Sunscreen can indeed 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 like "12M" (meaning 12 months), which is typically found on the packaging.

It's 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.