Makeup, indeed, has a shelf life
The problem with cosmetics is that they pick up bacteria from our
lips, faces and eyes, which we transfer to the cosmetic and then back
to ourselves -- or others, if we're sharing. The bacteria can cause
infections, rashes and irritations. The most dangerous thing is an eye
infection, which might lead to blindness.
The shelf life on makeup is about one year. Mascara should be tossed
after three months, experts say, and you should never add water or
--worse yet -- spit to dried mascara to reactivate it. That apparently
causes the bacteria to go wild.
Liquid foundation should be thrown away after six months; pressed
and loose powders, blushes and eye shadow are good for a year as are
lipsticks and lip gloss. But experts warn against leaving your
cosmetics, even new ones, in hot cars, which can accelerate bacteria
You should also avoid using cosmetics in areas they weren't approved
for, meaning don't use lip gloss or lip liner on your eyes. You can
transfer bacteria from your mouth to your eyes, or the products
themselves may not be safe for contact with your eyes.