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THIS SUNSCREEN ADVICE IS (MOSTLY) MYTH

Have you heard that you have to wait 15 to 30 minutes for skin to absorb sunscreen in order to get proper UV protection? That's not exactly true.
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MYTH: you have to wait 15 to 30 minutes for skin to absorb sunscreen before sun exposure in order to be fully protected against UV

MYTH: you have to wait 15 to 30 minutes for skin to absorb sunscreen before sun exposure in order to be fully protected against UV

No, you don't need to wait 15 to 30 minutes for skin to absorb sunscreen to be fully protected from UV when you step outside. That said, you do get better protection if you wait a few minutes, but for a different reason.

But first, please note the following terminology:

I use the term "non-mineral sunscreen" to identify formulas made with filters such as avobenzone, homosalate, Mexoryl XL, Tinosorb, etc. People usually call those formulas "chemical" sunscreens, but that makes zero sense because mineral filters – titanium dioxide and zinc oxide – are chemicals too. I could use "organic" sunscreen (non-mineral) and "inorganic" (mineral) sunscreen as terms instead – maybe next post?

One more thing: if you don't have time to read the details right now, zip to the end of the post for a 25-second, top-line video.

MYTH: YOU HAVE TO WAIT 15 TO 30 MINUTES FOR SKIN TO ABSORB SUNSCREEN BEFORE UV EXPOSURE

I saw this old nugget on a newscast just recently, and remembered that not every journalist gets a chance to chat with cosmetic scientists and chemists who actually formulate sunscreen.

Why does formulation insight make a difference? For starters, one might believe the most important element of sunscreen is its collection of UV filters, or maybe the level of protection printed on the label. But ask a chemist who makes sunscreen, and you'll get a response you don't expect. We'll get to that after the myth-busting bit...

FACT: SKIN DOES NOT NEED TO ABSORB SUNSCREEN INGREDIENTS FOR SUNSCREEN TO WORK EFFECTIVELY

Skin does not need to absorb sunscreen to be protected against UV exposure. But with mineral AND non-mineral formulas, waiting 10 to 15 minutes after application serves another important purpose.

Skin does not need to absorb sunscreen to be protected against UV exposure. But with mineral AND non-mineral formulas, waiting 10 to 15 minutes after application serves another important purpose.

Years ago, experts thought non-mineral sunscreen ingredients needed to penetrate the top layer of skin to be effective, but we now know that's not quite true. 

According to a study published in 2017 in the Journal of the European Academy of Dermatology and Venereology, "standard" sunscreen provides protection upon application and reaches optimal defence level in 10 minutes or less.

Non-mineral sunscreens, such as my fave, Vichy Ideal Soleil Sport SPF 60 Ultra-Light Refreshing Lotion for face and body (200mL, $29.95 at vichy.ca), absorb UV whether on skin or not. Skin does not "activate" sunscreen filters.

Non-mineral sunscreens, such as my fave, Vichy Ideal Soleil Sport SPF 60 Ultra-Light Refreshing Lotion for face and body (200mL, $29.95 at vichy.ca), absorb UV whether on skin or not. Skin does not "activate" sunscreen filters.

"Standard" sunscreen likely refers to formulas made with oxybenzone, homosalate, etc., because the "wait for skin to absorb ingredients" directive is usually in relation to non-mineral filters that work largely by absorbing UV rays. (They absorb UV even if not on skin, so why anyone thought skin had to absorb them first is a mystery.) Plus, mineral sunscreen formulas weren't great or as popular in the years leading up to 2017 as they are now.

The other thought back then – and now – was/is that mineral sunscreen filters work by reflecting UV and aren't absorbed by skin, so they're perceived as being immediately effective. (The reflecting/ absorption details aren't exactly true, but don't affect overall efficacy, so we'll leave them for another post.)

Access to the “Time Required for a Standard Sunscreen to Become Effective Following Application: A UV Photography Study" abstract and details requires a fee, but practiceupdate.com is a resource for medical professionals; a doctor has summarized the findings for readers. In addition, dermatologist Dr. Ashish Bahtia, Associate Professor of Clinical Dermatology at Northwestern University as well as a practiceupdate.com site author, posted the following take in the comments:

Through in vivo and in vitro testing, these authors determined that a standardized sunscreen formulation demonstrated immediate photoprotection after application and achieved photostability in 5 minutes. Similarly, in healthy, skin type III adults, the sunscreen effectively absorbed UV immediately upon application and was photostabilized in approximately 10 minutes. This debunks the “standard-of-care” educational message that patients should apply their sunscreen 30 minutes prior to going outside. In fact, the authors remind us that premature application can result in more opportunities for the sunscreen to rub off on clothing during activities of daily living!

There, now we all have an extra 15 minutes or so every day. 😉 No judgement if you're a hand-on-the-door "oh, I need sunscreen!" person – many of us are, and it's usually okay. When is it not really okay? Read on....

WHY SUNSCREEN LABELS SAY "APPLY 15 MIN BEFORE SUN EXPOSURE"

A directive to apply sunscreen 15 minutes before UV exposure appears on sunscreen packaging regardless of whether the formula is mineral or non-mineral, as per the above.               

A directive to apply sunscreen 15 minutes before UV exposure appears on sunscreen packaging regardless of whether the formula is mineral or non-mineral, as per the above.               

Here's the part of that wait-for-skin-to-absorb-sunscreen advice that has merit: although the reason is different, a 10 or 15-minute pause after application will actually give you better protection than applying on the fly.

Remember when I said that if you ask a cosmetic chemist who makes sunscreen what the most important part of sunscreen is, you'll get an unexpected answer?

According to cosmetic chemist Stephen Baldwin, who oversaw global formulation development of Coppertone sunscreens for 12 years, a sunscreen's film-forming components are just as important as the UV filters.

"You have to think of the skin as a wrinkled surface. It has a texture, hills and valleys and creases – even young skin, although it looks smooth," he says.

"To be effective, sunscreen needs to cover like a good paint, with a very even film, literally like a second skin to protect the peaks without puddling in the valleys. It has to be flexible and breathable and it has to be decently tenacious to achieve the necessary water-resistance for 80 minutes."

That suggested 15-minute wait gives sunscreen time to dry on your skin, to form that budge-resistant, second-skin protective barrier that won't smear or slide around as you move. And it's as important with mineral sunscreen as it is with non-mineral, even more so if you're going with a water-resistant formula before working up a sweat or swimming.

OVER TO YOU:

Have you heard that "wait for skin to absorb sunscreen" advice?

Do you deliberately wait at least 10 or 15 minutes after sunscreen application before heading outside?

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