We all recognize them on milk cartons. Expiration dates help us know when to throw out the product when it's no good to use anymore. But a large majority of cosmetics products don't have them.
I never know when to throw out a lip gloss or a mascara until it's completely dried out and useless. I asked my friend who went to beauty school how to know and she said I just had to use my best judgment. But recommended smelling it, if it smells different than when I bought it then it is a good sign to throw it out. Mascara is known to last the shortest amount of time. If you have any questions about throwing it out, just do it! It is better than risking infections.
Do you think there should be a law to require expiration dates? What tips do you follow?