How to Tell If Your Hair Products Have Expired

Whether it’s a gallon of milk or our favorite fragrance, we take expiration dates seriously. After all, just as past-its-prime food can make you sick, past-their-prime beauty products can be at best ineffective and at worst moldy, irritating, and full of enough bacteria to give even the bravest of us the heebie-jeebies. What you may not realize, though, is that there’s a whole other segment of your beauty routine that you may have been leaving out to spoil: your hair products.

Unlike food, the FDA doesn’t require expiration dates on makeup, skin, or hair products. But that doesn’t mean you’re on your own when it comes to figuring out if your mousse is past its prime. Here, experts explain what expiration means in the context of deep-conditioning masks, pomades, and shampoos, as well as how to figure out if any of your hair-care or styling products are kaput.

What does it mean for hair products to expire?

Cosmetic chemist Nick Dindio tells Allure there are two ways in which a hair product could expire: the quality can degrade and cause the product to no longer performs as well, or the product can become susceptible to contamination. “If the product loses some efficacy, there isn’t really a problem with using it after its expiration date,” he says — other than the potential for disappointment. However, if the product is contaminated with microorganisms, he says, then there could be health risks associated with using the product. 

Luckily, using a contaminated hair product doesn’t pose as great a threat as using contaminated skin care or makeup. “The risk is definitely lower with hair products since it isn’t on your skin or around sensitive areas like the eyes and mouth,” Dindio says. “But it’s still not a good idea to continue use.”

How do you read the expiration date code on hair products?

Unfortunately, it’s entirely up to each individual brand if it wants to print an expiration date on its products, so many simply don’t. That said, some brands opt to include a Period After Opening (PAO) mark on their packaging to indicate how long the product will remain fresh after the first use, and lots of hair-care brands have followed suit. To find the PAO mark, look on your product’s label for a small drawing of a container marked with a number and the letter M, typically on the back in the lower right-hand corner. The number is an estimate of how many months the product will maintain its quality after it’s been opened for the first time.