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If you read the title of this post and thought, “Wait, beauty products can go bad?,” you’re not alone.
The secret to this is hidden in plain sight, but is certainly easy to overlook. Take a peek at your moisturizer or blush packaging (we’ll wait). Do you see a small, nondescript jar icon with a number inside it? That’s it! This symbol is known as the Period After Opening, or PAO, and it indicates how long a product is good for (as in safe, effective and stable) once the formula hits the air.
But what exactly does it mean? Is it simply a ploy to encourage customers to buy more frequently, or is it actually dangerous to continue using past-due products? To get to the bottom of it all, we spoke with NYC dermatologist, Dr. Hadley King.
The first thing to get straight is the difference between the period after opening symbol and an expiration date.
Technically, the terms “expiration date” and “shelf life” are more or less interchangeable, and only need to be labeled on drug products like SPF, dandruff or acne products.
A product’s “expiration date” and “period after opening number,” however, are not interchangeable. Think of it as similar to food. Your food container may disclose a specific expiration date months or sometimes years in the future, but it may also say “use within x amount of days after opening.”
In terms of cosmetics, both expiration dates and PAO numbers are reached by undergoing shelf life and stability testing, Dr. King explains. This process involves observing how the product reacts to varying temperatures and humidity levels over periods of time.
Note: according to the FDA, this testing is considered the responsibility of the manufacturer, and therefore is not regulated.
This depends on the type of product you’re dealing with. “When skincare products expire, their active ingredients may be less potent and therefore less effective,” Dr. King cautions. “And it's also possible for yeast or bacteria to grow in outdated products, whether it’s a skincare or color product, which can then cause skin irritations or infections.”
This happens because the product’s preservative system, meaning its ingredients with preserving qualities that all work together, is only effective for this given period of time. Once the preservative system is weakened to a point that it can’t ward against contaminants, the formula is susceptible to these issues.
Products utilizing natural or plant-based ingredients often have a shorter shelf life and PAO than those formulated with more synthetic ingredients.
Packaging can also be a factor to consider. If you’re dipping your fingers into a product (like a jar of moisturizer), this can welcome additional bacteria or fungi. Components that touch your face and then go back into a product, such as mascara wands or doe foot applicators, can also prove a bacteria breeding ground.
“These bacteria, yeast and molds can irritate our skin and contribute to breakouts and even cause infections, especially when used around the eyes,” Dr. King says. If you’re experiencing any type of skin irritation or noticing any unusual smells from your past-due skincare or color products, it’s best to discontinue use. When in doubt, throw it out!
If you’re experiencing any skin irritation or noticing anything unusual about your products, even before they technically expire, it’s best to stop use immediately.
Items that have yet to be opened and exposed to air are less likely to be contaminated, Dr. King explains, but their expiration dates should still be considered. “Thinking about the age of unopened products is still important,” she says. “Ingredients can degrade and become harmful or irritating to your skin. Degradation is less likely when products are not exposed to air, heat and light, but can still happen over time.”
Still, think of it like the unopened box of chocolate that’s been sitting at the back of your pantry for a few months too many. It probably won’t make you sick, but it’s surely not as delicious or appealing as it once was! So, even if your expired products haven’t developed harmful contaminants, Dr. King says that they can be unpleasant to use. “Particles can clump together or come out of solution, or even in unopened containers, products can dry out over time.”
When it comes to skincare products, heat and humidity can make for an unstable environment, so they should be stored in a cool, dry place. “Beauty refrigerators can be an option to extend the shelf life of some of these products,” Dr. King suggests. “The colder temperature will also enhance the soothing sensation of products and will constrict blood vessels, which can decrease puffiness and redness.” Just be sure to keep an eye on them, as Dr. King notes lower temperatures can affect the texture and spreadability of some products. Just as a note: The ideal beauty refrigerator temperature is around 60 degrees Fahrenheit, whereas a typical refrigerator in your kitchen runs at about 40 degrees.
Makeup products should also be stored in cool, dry places, but it might be unpleasant to apply ice-cold foundation (it will also probably mess up the consistency of the formula). For makeup, Dr. King says that liquid products should be replaced after six months, while dry powders can be kept for two years. Mascara and liquid eyeliners, however, should be replaced after three months.
Essentially, the PAO and shelf life or expiration of products depend heavily on the kind of product and its ingredients, the conditions in which it’s stored, and the packaging. As Dr. King advises: “When all else fails, use the sniff test— if it smells funky, throw it out!”