How Free Radicals From UV Actually Damage Your Skin
The molecular story behind sunburn and photoaging.
Much of UVA's harm is indirect: it generates reactive oxygen species (free radicals) that damage DNA, lipids and collagen, on top of the direct DNA damage caused by UVB.
Because roughly 95% of the UV reaching the ground is UVA, much of the daily oxidative stress on skin comes from these deeper-penetrating, free-radical-generating rays.
Questions we get a lot
How does UV light age and damage skin?
UVB is absorbed by DNA in surface cells, causing direct mutations that can lead to skin cancer. UVA penetrates deeper, generating free radicals (reactive oxygen species) that damage DNA, collagen and elastin — producing wrinkles, sagging and dark spots. The damage accumulates over a lifetime, so daily protection pays off.
What are reactive oxygen species and why do they matter?
Reactive oxygen species (ROS), or free radicals, are unstable molecules that steal electrons from DNA, proteins and lipids, damaging cells. UV exposure floods skin with ROS faster than its natural defenses can neutralize them, and that oxidative stress drives much of UV-related aging and contributes to skin cancer.
Do antioxidants in skincare help against UV free radicals?
They can complement, but never replace, sunscreen. Topical antioxidants such as vitamins C and E help quench some of the free radicals UV generates, reducing oxidative damage. Used under a broad-spectrum SPF, they add a layer of defense — but only sunscreen blocks the UV that creates those radicals in the first place.
r/SkincareScience: 'How exactly do free radicals from the sun damage skin?'