When your skin is exposed to sunlight, it releases a natural substance called nitric oxide that helps calm down harmful molecules in your skin and keeps things balanced — but this doesn't work right if you have long-term skin inflammation.

When there's less sunlight in winter or far from the equator, your skin makes less nitric oxide from sunlight, which can upset the balance in your skin and make conditions like psoriasis or eczema worse.

Some light-based treatments might help calm down angry, inflamed skin by copying how sunlight naturally balances certain chemicals in your skin, which could make conditions like eczema or psoriasis feel better.

Sunlight can create harmful molecules in your skin, but your body naturally produces nitric oxide to balance them out—this balance keeps your skin healthy.

Sunlight’s UV-A rays might help your blood vessels relax by turning a substance in your skin called nitrite into nitric oxide, even without your body using its usual method—this could be why you feel that warm, tingling sensation in the sun.

In mice, certain antioxidants reduce skin swelling after sun exposure, which means free radicals cause inflammation—but they don’t help sunblock stop immune suppression, so these two effects happen through different paths.