Do We Need Sunscreen In Winter, Really?

It’s Q&A Day at 10almonds!

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In cases where we’ve already covered something, we might link to what we wrote before, but will always be happy to revisit any of our topics again in the future too—there’s always more to say!

As ever: if the question/request can be answered briefly, we’ll do it here in our Q&A Thursday edition. If not, we’ll make a main feature of it shortly afterwards!

So, no question/request too big or small 😎

❝I keep seeing advice that we shoudl wear sunscreen out in winter even if it’s not hot or sunny, but is there actually any real benefit to this?❞

Short answer: yes (but it’s indeed not as critical as it is during summer’s hot/sunny days)

Longer answer: first, let’s examine the physics of summer vs winter when it comes to the sun…

In summer (assuming we live far enough from the equator to have this kind of seasonal variation), the part of the planet where we live is tilted more towards the sun. This makes it closer, and more importantly, it’s more directly overhead during the day. The difference in distance through space isn’t as big a deal as the difference in distance through the atmosphere. When the sun is more directly overhead, its rays have a shorter path through our atmosphere, and thus less chance of being blocked by cloud cover / refracted elsewhere / bounced back off into space before it even gets that far.

In winter, the opposite of all that is true.

Morning/evening also somewhat replicate this compared to midday, because the sun being lower in the sky has a similar effect to seasonal variation causing it to be less directly overhead.

For this reason, even though visually the sun may be just as bright on a winter morning as it is on a summer midday, the rays have been filtered very differently by the time they get to us.

This is one reason why you’re much less likely to get sunburned in the winter, compared to the summer (others include the actual temperature difference, your likely better hydration, and your likely more modest attire protecting you).

However…

The reason it is advisable to wear sunscreen in winter is not generally about sunburn, and is rather more about long-term cumulative skin damage (ranging from accelerated aging to cancer) caused by the UV rays—specifically, mostly UVA rays, since UVB rays (with their higher energy but shorter wavelength) have nearly all been blocked by the atmosphere.

Here’s a good explainer of that from the American Cancer Society:

UV (Ultraviolet) Radiation and Cancer Risk

👆 this may seem like a no-brainer, but there’s a lot explained here that demystifies a lot of things, covering ionizing vs non-ionizing radiation, x-rays and gamma-rays, the very different kinds of cancer caused by different things, and what things are dangerous vs which there’s no need to worry about (so far as best current science can say, at least).

Consequently: yes, if you value your skin health and avoidance of cancer, wearing sunscreen when out even in the winter is a good idea. Especially if your phone’s weather app says the UV index is “moderate” or above, but even if it’s “low”, it doesn’t hurt to include it as part of your skincare routine.

But what if sunscreens are dangerous?

Firstly, not all sunscreens are created equal:

Learn more: Who Screens The Sunscreens?

Secondly: consider putting on a protective layer of moisturizer first, and then the sunscreen on top. Bear in mind, this is winter we’re talking about, so you’re probably not going out in a bikini, so this is likely a face-neck-hands job and you’re done.

What about vitamin D?

Humans evolved to have more or less melanin in our skin depending on where we lived, and white people evolved to wring the most vitamin D possible out of the meagre sun far from the equator. Black people’s greater melanin, on the other hand, offers some initial protection against the sun (but any resultant skin cancer is then more dangerous than it would be for white people if it does occur, so please do use sunscreen whatever your skintone).

Nowadays many people live in many places which may or may not be the places we evolved for, and so we have to take that into account when it comes to sun exposure.

Here’s a deeper dive into that, for those who want to learn:

The Sun Exposure Dilemma

Take care!