Does sunscreen expire and how can I check if mine is still good?

Yes, sunscreen expires because active ingredients break down and lose SPF protection. Check for an expiration date — most are good for three years from manufacture. If there’s no date and you can’t remember when you bought it, toss it. Also check texture and smell: if it’s separated, lumpy, watery, or smells off, it’s done. Don’t risk it — fresh sunscreen is cheap compared to skin damage.