Sunscreen question?!

Sunscreen question?

I went to discovery cove in August, and they gave us some free sunscreen. Is that sunscreen still good to use? It's about 10 months old, but hasn't been opened.

I had this discussion before. The active chemical ingredients in sunscreen are relatively stable -- mostly aromatic organic compounds that absorb UV light. They should not and do not decompose with time or light or moderate heat. So why does it have an expiration date? Because it is an "over-the-counter" product. It usually has an expiration of 3 years because that is the longest the manufacturer can have tested that it still does what it suppose to do. They don't want to put 10 years or 50 years, because they would then have to prove it. But the ingredients should not spoil.
That being said, sunscreen and sunblock are similar to cosmetic formulations -- they are colloidal mixtures. So with time and heat, they tend to separate so it wouldn't look creamy any more. However, if you don't care whether it looks or feels creamy, you can place it on your palms and re-mix it. The basic ingredients won't stop blocking the UV light.