Now that you know how important it is to wear sunscreen when you go outside (even on cloudy days), you may be thinking about the bottles you have from last year. Are they still good or do you have to shell out more money and buy new ones?
Here's the deal. Sunscreen supposedly can last up to 3 years, but if it wasn't stored in a cool, dry place with the cap tightly closed, it should be tossed out. The active ingredients in sunscreen can deteriorate and lose effectiveness if exposed to high temperatures, so if you're not sure, I'd spring for some new bottles. How many times have you left the bottle to bake in the car while you were out hiking?
Your old sunscreen bottles should have expiration dates. If they haven't expired yet, you should check out the consistency. If it has changed or looks discolored, is lumpy, or smells funky - ditch it and buy some new sunscreen. I'd opt for skin safety over saving a few bucks. It is probably more economical in the long run.