When to do away with your makeup.

Beauty hoarders, consider this is your tough love wake up call. While it can be tempting to hold on to every purchase for as long as possible, cosmetics do have expiration dates. Ignoring them could result in product reformulation (ick), or worse, bacteria buildup. That's right—your makeup could make you sick. When the whole point is to put your best face forward, why risk subjecting yourself to a day in bed?

"Good quality makeup and makeup tools are an investment—it's like a wardrobe for your face and skin that you wear every day," makeup mogulBobbi Brown told us when we asked for her expert opinion on the matter. "By taking care of the items, you get a better return on the investment. Also, by regularly cleaning your makeup tools your skin will be cleaner and reduce the likelihood of breakouts." Hear, hear. But with all of the conflicting shelf life info flying around, who can make sense of it all? Luckily, Brown offered to break it down by the numbers. Get your definitive, no-nonsense guide below—and have your trash can at the ready.

How to keep your brush clean.
"Take a drop of brush cleaner or very gentle soap in your palm and swirl the bristles around until they're sudsy. Rinse thoroughly, and then squeeze out excess moisture with a clean towel. Reshape the brush head if needed and let the brush dry with the bristles hanging off the counter edge so they keep their shape—this is very important," 

"How can I tell if it's time to throw away my old cosmetics and makeup? "

Cosmetics - both skin care and makeup -aren't meant to grow old with you. "Products are developed to last a year or two," says Peter Pugliese, M.D., a skin physiologist in Reading, Pennsylvania. However, contamination can occur at any time, since makeup is always in contact with germ-prone areas like your eyes, mouth and fingers. In general, always toss anything that has changed color or consistency or has a bad odor. Otherwise, use these guidelines to assess the shelf life of common beauty products.

• 1. Most powders, concealers and lip balms are anhydrous (they don't contain water), so they can last for a couple of years, says Dr. Pugliese.
• 2. Cleansers and moisturizers often contain fatty acids, which can turn rancid quickly. Toss after six months.
• 3. Multiuse products such as 3-in-1 sticks and creams can spread germs from lips to eyes and cheeks. Wipe the surface before switching areas, and discard or replace after six months.
• 4. Pencils can last several years unless you wet the tip with saliva or water. To be safe, sharpen before each use.
• 5. Mascara should be tossed after three months without fail. The tube is a breeding ground for bacteria," says Dr. Pugliese.
• 6. Foundations can last up to a year if you keep your fingers away from the bottle. Instead, use a sponge to apply.
• Store cosmetics in a cool, dry place outside the bathroom to extend their shelf life.