I decided to write this article because I work in the cosmetic industry and I see women buy tons of makeup but are not conscious of how long they should keep the products, which really isn't good for your skin in sensitive areas.

How to identify the shelf life symbol? This is usually located on the back of your product next to the barcode. You will see an open jar that may have 6M or 12M as demonstrated below, M=Months this is how long you should keep a product before you discard it.

Mascara: Toss your mascara after 3 months. Mascara has the shortest life span of all makeup because the risk of transferring bacteria back and forth from your eye into the mascara tube is so great. If your mascara starts to dry out before its 90 days are up, throw it away. Don't add water or saliva to your mascara to rewet it. Doing so will only increase your chances of getting an eye infection.
Eye Pencils: Eye pencils can be kept up to 2 years. To make sure you're using a clean tip, sharpen before each application.
Eye Shadows: Keep your applicators clean and your liquid shadows should last 12 months. Powder shadows will keep up to 2 years.

Lipsticks: You can stow your tube lipsticks and your lip pencils for 2 years. As with eye pencils, sharpen your lip pencils before each use.
Blushes and Powders: Discard your cream blushes after a year, powder blushes and powders after 2 years.
Foundation and Concealers: Moisturizing foundations and stick concealers can hang around for 18 months. A 12 month shelf life applies to both oil-free foundations, which can dry out quickly, and liquid concealers.

Using clean brushes and sponges will help lengthen the life of your cosmetics. Be sure and wash or replace your applicators frequently.