Do you know how to check your hair care products to ensure that they have not expired? At the moment, there’s no law requiring hair products to have any expiration dates on them, but hair products do in fact expire.
Most sealed products are considered to be safe to use for up to three years as long as they are stored in a cool dark place. Once they are opened they are susceptible to all kinds of microorganisms. Which is why many product companies chose to include a Period After Opening (PAO) mark on their packaging. Look on your product's label for a small drawing of a container marked with a number and the letter M. The number is an estimate of how many months the product will maintain its quality after it's been opened for the first time.