Many makeup experts will tell you that nail polish is expired and ready to be tossed two years after opening. Polish may last much longer than this, however, or meet an earlier death depending on where it is stored. Nail polish is very different from other types of makeup, making it much harder to determine an expiration date.
Why Makeup Expires
Cosmetics expire because they are exposed to the bacteria on your skin when you brush them on your face and then dip the brush back into the makeup. In some cases, such as mascara, you even store the applicator inside the product between uses. The result is bacteria buildup in the makeup, deteriorating the cosmetics and making them potentially unhealthy to use. With potent ingredients like formaldehyde, nail polish does not harbor bacteria and never becomes unsafe to use. It will, however, separate, change color and become gooey or dried out when it has passed its prime. Adding a little nail-lacquer thinner can sometimes make clumpy polish usable again.
Best Storage Practices
For the longest life possible, cap nail polish tightly and store it in a cool, dry place away from sunlight and humidity. The bathroom is the worst place to store your polish due to the fluctuating temperature and humidity. Storing bottles upright in the refrigerator will slow the discoloration that occurs with aging but is not recommended as refrigerators use an electric motor and nail polish contains flammable ingredients.
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