Short answer: both can protect you well. What matters for riders and runners is how each one behaves when you sweat, wipe your face and keep going for hours.
Sunscreen labels sort products into two camps: mineral (sometimes called physical) and chemical (sometimes called organic). Here's what the difference means in motion, without the marketing.
How each one works
- Mineral sunscreens use zinc oxide and/or titanium dioxide. They sit on the surface of the skin and form a barrier against UV light, as MD Anderson Cancer Center explains. Zinc oxide on its own covers both UVA and UVB.
- Chemical sunscreens use filters that are absorbed into the upper layers of the skin, where they take in UV radiation and turn it into a small amount of heat. Most formulas combine several filters to cover the full UV range.
What matters when you're moving
|
|
Mineral |
Chemical |
|---|---|---|
|
Where it sits |
On the surface of the skin |
Absorbed into the upper layers |
|
When it works |
As soon as it's applied |
Usually advised to apply in advance |
|
In sweat |
Particles don't dissolve, so it tends to stay where you put it |
Filters can travel with sweat |
|
Near the eyes |
Often preferred by people whose eyes sting during exercise |
A common cause of stinging when sweat runs |
|
Feel and finish |
Traditionally thicker, and can leave a white cast |
Usually lighter and clear |
|
Sensitive skin |
Often recommended for reactive skin |
More likely to irritate some people |
No option is perfect. Mineral formulas have historically been harder to make feel light, and some leave a white cast on darker skin. Chemical formulas are often lighter and are widely made in water-resistant versions. A good formula of either type beats a bad one, and the best sunscreen is the one you'll actually wear and reapply.
The sweat-in-the-eyes problem
If you've ever ridden half-blind down a descent with stinging eyes, you know why this matters. The cause is usually sunscreen travelling with sweat from the forehead into the eyes. Chemical filters are dissolved in the formula, so sweat can carry them. Mineral particles don't dissolve, so they're less inclined to move. Mineral isn't a guarantee: anything in your eye will irritate it. But many athletes find the switch makes a real difference.
Why SunMer chose mineral
We built the Day Shield Sun Stick SPF50 on 100% mineral filters for three reasons:
- Broad-spectrum UVA/UVB protection from filters that start working the moment you apply them.
- Staying put on a sweaty face, so protection stays on the nose and cheekbones instead of running into your eyes.
- A formula gentle enough for sensitive areas such as the nose and ears, and COSMOS Natural certified.
We then worked on the thing mineral sunscreens are known for getting wrong: the feel. The stick format means a thin, even layer that blends in, rather than a thick cream.
How to choose, whatever you buy
- Look for broad-spectrum (UVA and UVB) and a high SPF for long days.
- If your eyes sting during exercise, try mineral, at least on the forehead and around the eyes.
- If you have reactive skin, try mineral and fragrance-free.
- Choose a format you'll actually carry and reapply.
- Whatever you choose, apply enough and reapply after sweating or towelling.
More stories: Founders Story, Why a stick?, The SunMer SPF50 Stick
