Sunscreen is messy. Some formulas feel like chalk. Others vanish into the skin like water. You get lots. Lotion. Spray. Stick. Gel. It is a confusing carnival of acronyms. SPF 50? 70? Broad spectrum? What does any of it mean when the beach is waiting?
With Memorial Day around the corner we decided to ask the people who actually study this stuff. Dermatologists and chemists explained how these creams work, why you should probably keep putting them on, and why things might change in America soon.
The mirrors and the sponges
Ultraviolet radiation destroys skin DNA. It causes cancer. It creates wrinkles. Simple physics, really. Sunscreen fights this in two distinct ways. It blocks the light. Or it eats it.
“Mineral” sunscreens use zinc oxide or titanium dioxide. Think of these as tiny mirrors. David Fisher from Harvard calls them nanoparticle reflectors. They bounce UV and visible light off the skin. This is why they look white. Pastey white. Gross? Maybe. But effective. Interestingly, they do absorb a bit too, even though we think of them as blockers.
Chemical sunscreens operate differently. They absorb specific UV wavelengths. Kerry Hanson at UC Riverside says the molecules take the UV light and convert it to heat. That’s it. Poof. Gone. They are clear. They don’t leave a ghost mask on your face. People like the look. Do they like the feel? Debatable.
The SPF blind spot
Here is where most people get tripped up. SPF stands for Sun Protection Factor. It measures how well you are protected from burning. Specifically. It measures protection from UVB rays. Those are the 280-to-315 nanometer wavelengths that turn your nose red and blister your shoulders. UVB has its uses. Vitamin D synthesis. But mostly? It burns you.
Manufacturers have focused on UVB for years. Big mistake, argue some scientists. UVA rays range from 315 to 400 nanometers. They penetrate deeper. They cause aging. They likely raise skin cancer risk. SPF says nothing about UVA. A high SPF number might stop a burn while UVA still cooks your collagen.
You need “broad spectrum.” In theory this means you are shielded from both UVB and UFA. But how good is it? We don’t know. Not really. The US has no scale for UVA protection like Europe has the PA++++ rating system. AJ Addae at UCLA notes this gap. The FDA just checks a box. No number. Just a label.
“It isn’t an SPF-like measure.”
Is there a problem? Yes. Can we measure it here? No.
Safety vs. Fear
There is anxiety in the air lately. Consumer groups are nervous. Some spray sunscreens can actually catch fire. Others have been tainted with benzene. A known carcinogen. Bad.
Then there is the reef problem. Certain chemicals hurt coral. Bad.
In 2019 the FDA flagged several common ingredients—oxybenzone, octocrylene, ecamsule—as possibly absorbing into the blood stream. Sounds scary. Does it cause harm? We have no proof yet. Theresa Michele from the FDA was clear. Insufficient data isn’t a verdict of guilt. It’s just a request for more data.
Meanwhile, skin cancer doesn’t stop because you’re worried about nanoparticles in your bloodstream. Experts stress that wearing any sunscreen beats wearing none.
Buy what you will touch
How do you choose? Stop overthinking the chemistry.
“The best sunscreen is the one you’ll actually wear.”
Addae says find SPF 30 at minimum. Find a texture you don’t hate. If you find the sensation revolting you will wash it off. If you wash it off it doesn’t matter how good the science is. Addae is working on changing zinc oxide particle shapes. The goal? Less white cast. Better for darker skin tones.
For the beach? Hanson wants water-resistant and broad spectrum. Apply a lot. Too much of us use a dime-sized amount on a football-sized body. You need a shot glass of sunscreen to cover an adult fully. Paint yourself like you’re latex-dipping furniture. Make a film.
We are limited by FDA rules here in the US. They treat sunscreen like a drug. Europe and Asia treat it closer to a cosmetic. They get new ingredients. We don’t. Last year the FDA looked at bemotrizinol. It’s popular elsewhere. It hasn’t been approved since 1999? Imagine that. If this gets green-lit it would be a big shift.
But you know what? Hats work. Shirts work. Staying in the shade works. Fisher says he cannot stress enough the value of physical barriers. Sunscreen is the backup. The first line of defense is simply avoiding the sun.
