We pay a lot of attention to the expiration dates on food items. Meat, cheese, eggs, milk and other products are often scrutinized for their expiration dates. And rightly so, because bad food can make us sick. But, for instance, so can bad medicine, and we also keep close tabs on that.

There is another product that we should be beware of, as well, that can easily spoil and be rendered useless. Sun block. Checking the expiration dates is important, but there are other important factors.

Experts say tubes and containers of sun block or sunscreen that are left in the heat, like in a hot car for weeks at a time, can lose their effectiveness. And let's face it: an ineffective sunscreen lotion can be dangerous.

The standard expiration date for all sunscreens is two years, but containers of the stuff left in a cool and dry spot, like a closet, can last for up to five. All natural sunscreens, made with zinc and titanium, can last longer than sunscreen products made with chemical compounds.

If you have chemical sunscreen that you fear is degraded, because it has become gritty or runny, and it's ALL you have available, you can still use it if it's all you have that day. Just make sure you apply it more abundantly and more often.