I have some sample packets of suncreen. The expiry date was about 2 years ago. Will it still work? What is the active ingredient in sunscreen and does it really lose potency? 
Yes, it does. Sunscreen doesn’t last very long, does it? I wouldn’t use it past the date on the package.
BIG WARNING!!! Sunscreen DOES expire, and it’s useless after it does. When I was a lot younger my family went to a tropical island and our sunscreen had expired. We all wound up with incredibly nasty burns – my sister had a blister on her back almost an inch high.
Not only do sunscreens expire but any cream or cosmetic can degrade over time - ever use an old hand lotion and it was all runny and slimy - throw it away!