Has your medicine cabinet seen a good purge yet this decade?

Hygiene and makeup products can and will go bad. Keep something too long and it could become ineffective or even start growing potentially harmful bacteria -- especially eye products, since we use them around such sensitive areas of the body.

But knowing when exactly you need to throw out all those items in your bathroom can get confusing. So we scoured the Internet for these general guidelines and checked them with Dr. Jessica Krant, M.D., founder of Art of Dermatology in New York City. Of course, not every lotion or mascara is created equal, and not every one of the below has the potential to make us sick (perfume, for instance, might lose its smell but it probably won't grow bacteria before you use it up, according to Krant). While exact times can vary by brand or variety, here are some handy guidelines to kickstart your spring cleaning:

Graphic by Jan Diehm for the Huffington Post.

A lot of cosmetics come with expiration dates encoded next to an icon of an open jar. The number next to "M" or "Y" indicates the number of months or years a product should be kept, and ultimately trumps the guidelines above.

Where most of these products are concerned -- especially makeup -- refraining from sharing with friends can cut back on the spread of bacteria. Storing personal products in cool, dry places (read: not the bathroom!) can help prolong their lifespans and prevent bacterial growth, too -- inversely, storing products incorrectly can cause them to spoil far before any printed expiration. This is especially true for some "all natural" concoctions, whose plant-based components, although pleasantly scented, can act as a magnet for microbes. And you'll always want to discard products with an unusually foul smell. Yuck.