Mineral vs chemical sunscreen: what we know and what we don’t

01 / The short answer

Both protect. What differs is what we know about each.

02 / How each one works

Less different than the label suggests.

The usual story is that chemical filters absorb UV while mineral filters reflect it like a mirror. That's only partly true: zinc oxide and titanium dioxide also work mostly by absorbing UV and reflect only a small share. Cole et al., 2016 ↗

What does change is how they feel. Chemical sunscreens (avobenzone, octocrylene, homosalate…) tend to be lighter, clear and easy to spread. Mineral ones can leave a white cast, especially on darker skin, but they tend to irritate less and sting the eyes less. Zinc oxide covers UVB and UVA well; titanium dioxide protects less against part of UVA, which is why many formulas combine them.

Either way, real protection depends on the amount: almost everyone applies far less than the amount used to test SPF. NHS ↗

03 / Absorption

What the FDA measured.

In 2019 and 2020 the US Food and Drug Administration measured in controlled trials how much filter reaches the blood. Six common chemical filters (avobenzone, oxybenzone, octocrylene, homosalate, octisalate and octinoxate) went above the level at which the FDA asks for more safety studies after a single application. Matta et al., JAMA 2019 ↗ Matta et al., JAMA 2020 ↗

Being absorbed doesn't make a filter dangerous. It means more data is needed. That's why the FDA proposed recognising only zinc oxide and titanium dioxide as safe and effective on current data, and asked for more studies on the rest without withdrawing them. FDA 2019 ↗ The same trials recommended that people keep using sunscreen.

04 / Endocrine disruptors

What's been seen in the lab, and what hasn't in people.

Some filters, especially oxybenzone (benzophenone-3), show hormonal activity in cells and in animals exposed to high doses. In people, with normal use, there's no evidence of harm. Studies are few and research continues.

As a precaution, the European Union lowered the maximum allowed concentration of oxybenzone and octocrylene in cosmetics in 2022. Regulation (EU) 2022/1176 ↗ That's how regulation works: when there are reasonable doubts, exposure is limited while more data arrives.

05 / How to choose

Shade first. Then the sunscreen you'll actually wear.

The WHO ranks protection like this, with sunscreen as a complement rather than a substitute: WHO ↗

1. Time: short sessions, below your burn time.
2. Shade during high-UV hours.
3. Clothing, a hat and sunglasses: they protect without your skin absorbing anything. UPF-rated clothing is the most reliable.
4. Sunscreen on the skin still in the sun: broad spectrum, SPF 30 or higher, applied generously and reapplied every two hours and after swimming.

If your skin is sensitive, you're choosing for children or you'd rather avoid filters that are absorbed, look for a zinc oxide mineral sunscreen. If mineral means you won't wear it, a well-applied chemical sunscreen protects far better than none.

06 / What Taiyo does

It will never suggest burning without sunscreen.

Taiyo respects each person's choice about sunscreen, but it will never suggest staying in the sun unprotected beyond half your burn time. With or without sunscreen, what harms skin is burning. If you don't want to use sunscreen, the app suggests short sessions and tells you when to find shade or cover up.