When you buy a gallon of milk at the store, you have an expiration date to determine when you should replace it. But, what about your liquid foundation? There are no laws requiring cosmetics to have expiration dates, so you can’t refer to the label to determine if your makeup is still good. From the moment you open your tube of mascara or your bottle of foundation, the effectiveness of the product decreases. Not to mention, its ability to fight bacteria decreases. Makeup already contains bacteria when you first buy it, and every time you open or touch it, you add more. Ready to find out if you should be purging your makeup bag? I have compiled a list of makeup products, their shelf life, and ways to preserve them so that they will last a little longer.