According to board-certified dermatologist Kiran Mian, D.O., phenoxyethanol is a preservative that's used in cosmetics, perfumes, and toiletries. It's colorless, oily, and has a rose-like odor. Chemically speaking, it's an ether alcohol that's naturally found in green tea. But most of the phenoxyethanol you'll come across is synthesized in a lab. 

On that note, you probably use this chemical more often than you think. About 23.9% of personal products contain phenoxyethanol1, so it's a pretty common preservative. It's likely in most of your products, from leave-on cosmetics (like lipsticks) to rinse-off formulas (like cleansers).

Although it may sound unpleasant, your cosmetic products double as the perfect home (and food) for harmful microorganisms. It's all thanks to water and organic/inorganic compounds2, which is found in basically every product. 

As a preservative, phenoxyethanol is ultimately used to extend a product's lifespan. Its antimicrobial and stabilizing properties protect the formula from spoilage, which would render the product useless—and unsafe. This increases the length of time you can enjoy the product without any issues. (It's still smart to check the expiration date, though!)

Phenoxyethanol is generally recognized as a safe, well-tolerated preservative3. Yet, there have been a few reports of this substance causing adverse effects. 

In a 2010 case study, a woman developed an allergic reaction—in the form of hives and anaphylaxis—after using a skin care product with phenoxyethanol. The researchers did a specific phenoxyethanol skin test and found that she was allergic to the preservative. There was also a 2015 report of phenoxyethanol causing irritation. The preservative, which was applied via ultrasound gel, led to contact dermatitis.  

Also, in 2008, the FDA issued a warning "for a nipple cream containing phenoxyethanol and chlorphenesin, another preservative [that causes] central nervous system effects, as the two ingredients could synergistically increase the risk of respiratory depression in nursing infants," says Cheung. 

Finally, in animal studies, phenoxyethanol has caused negative effects at very high doses. However, any potential toxicity happens at exposure levels much higher—around 200 times more3—than what's used in cosmetics. 

"Even though phenoxyethanol is regarded as low-risk, you can be sensitized to any chemical," explains Cheung. So, if you have sensitive skin, she recommends proceeding with caution when using any new skin care products—including those with phenoxyethanol. 

If you think you have a phenoxyethanol allergy, do a patch test first, suggests Mian. Apply a small amount to your inner wrist. Keep an eye on the area for 24 hours. You can keep using the product if you don't develop a reaction. If you do have a reaction, remember that it could be caused by any ingredient in the formula. Your best bet is to visit your dermatologist to try to pinpoint the culprit.