Toss your foundation ... every six to eight months, or as soon as it shows signs of discoloration or uneven consistency.
Those are signs that the foundation could be contaminated with bacteria from a make-up brush or even your fingers. And bacteria, says dermatologist Joel Schlessinger, M.D., president emeritus of the American Society of Cosmetic Dermatology and Aesthetic Surgery, can cause breakouts and contribute to painful skin infections. "Fortunately, foundation is generally pretty stable," says Dr. Schlessinger. "But if you've noticed that you're breaking out a lot, and cleaning your makeup brush doesn't help, your foundation may be contaminated, meaning it's time to toss it."