Chemical Sunscreen (Sun Care)

Chemical sunscreen uses carbon based filter molecules dissolved into the formula rather than suspended in it. Each molecule takes in ultraviolet energy, shifts to a higher energy state and drops back, releasing the difference as an almost undetectable amount of heat. Because they dissolve, the finished film is thin, clear and even. This is the whole reason this family dominates daily wear and everything sold on invisibility.

No single filter does the entire job, so formulas are built as sets. Avobenzone covers long wave UVA and breaks down under light within about an hour unless it is stabilized, usually by octocrylene. Filter lists read like recipes. Octisalate, homosalate and octocrylene handle UVB and hold the blend together. Photostability, meaning how well a filter set survives the light hitting it, is the real quality difference between two bottles carrying the same SPF number. Outside the United States newer filters such as bemotrizinol and bisoctrizole are approved and hold up better. The same brand's European bottle is often a different formula.

Mineral Sunscreen is the counterpart, visible but inert on the surface. Body Sunscreen most often uses chemical filters for water sports because the film clings better in surf. Face Sunscreen relies on them for anything that has to sit under Foundation without shifting shade.

Deeper skin tones get the cleanest result here, with no gray cast at full application. Swimmers and runners benefit from filters that hold in water. Daily wearers under makeup gain most of all, since a chemical film sits flat where a mineral one grabs pigment. Very reactive skin and skin around the eyes are where these formulas cause trouble, as several filters migrate with sweat and sting.

Read for a stated UVA filter rather than trusting a big SPF number, and use the European UVA in a circle or a Japanese PA+++ mark as shorthand when you see one. Give it 15 minutes before sun exposure so the film sets evenly. Keep the bottle out of heat, which accelerates filter breakdown, and reapply every two hours in real sun, since photodegradation happens on your skin as well as in the bottle.