Don't keep make-up too long.
As a general rule, most make-ups have a shelf life of 1-2 years. After that, the oils in the make-up begin to spoil and the chemicals begin to make down, resulting in potentially harmful effects on your skin. Mascara should be changed every 6 months, since the eye area is more prone to infection. With that in mind, even if your favorite lip color or eyeshadow is being discontinued, don't buy a ton with the purpose of hoarding them for several years down the road.

Never share make-up or applicators.
This goes without saying, but sharing make-up and make-up tools, especially those that are near the eye area, can lead to the spread of infections. It's especially important not to share applicators.

Check the ingredients.
All make-up you buy, particularly foundation, which is applied more liberally, mean non-comedogenic. These substances are less likely to clog your pores, resulting in fewer acne breakouts or blackheads.

Always clean your make-up off at the end of the day.
It's easy, especially when you're tired, to go to bed without washing your face. However, not clearing your skin of your make-up can result in clogged pores and irritated eyes. No matter now tired you are, you should always wash your face at the end of the day. This will also help to prevent breakouts.

Because some make-up products, especially eye makeup and some thicker foundations, are harder to remove with just a facial cleanser, it's important to also use a make-up remover when taking your make-up off.

Keep your make-up applicators and tools cleaned.
Make sure you clean your brushes, sponges, blush brushes, powder puffs, and so forth regularly. Or, replace them every few months. The residue in leftover cosmetics that accumulates on your applicators is a breeding ground for germs and harmful bacteria. You can use mild liquid detergents meant for wool and silks to wash your tools.

Prep your skin before applying make-up.
Prepare your skin for make-up by cleaning off any make-up you may already have on; don't be tempted to "freshen up" your make-up for the evening by layering it on top of the make-up you wore all day. Instead, clean your make-up off and then apply a new coat.

In addition, you should always use a moisturizer before you put your make-up on. Not only does it keep your skin from drying out, it also provides a protective barrier against the chemicals found in make-up that may irritate your skin.

If you have sensitive or oil-prone skin, make sure the moisturizer you use is designed specifically for sensitive skin and doesn't contain oil or alcohol.

Your moisturizer should also contain an SPF (sun protection factor) of at least 15, which will help protect your skin from the harmful effects of the sun's rays.

By using the right make-up and following a skin-care routine, make-up won't harm your skin.