(Back to Basics)

PCA Is The Most Powerful Hydrating Ingredient That No One Is Talking About

The experts shine a light on its many forms & benefits.

With new products, brands, and categories popping up every day, beauty can be a bit overwhelming. Back to Basics is our rudimentary beauty series that serves as your crash course on the science behind some of the best formulations in the game.

When it comes to skin care’s most powerful hydrators, chances are you’re already familiar with humectants (aka, moisture-binders) like hyaluronic acid and ceramides, and if you’ve been following this series at all, perhaps more under-the-radar ingredients like urea. But if you’re looking to up your skin’s moisture levels while calming eczema rashes, improving its barrier function, or controlling oil and shine without stripping it, there’s another lesser-known humectant to get to know: PCA, and its many, many derivatives.

PCA stands for pyrrolidone carboxylic acid (try saying that three times fast), and it’s an amino acid that’s naturally found in the body, primarily within the stratum corneum, or the outermost layer of the skin.

“PCA is a major portion of the skin’s natural moisturizing factor, or NMF,” explains Bryan Barron, director of skin care research at Paula’s Choice. “The NMF regulates hydration in the skin’s surface layers. As skin cells move from the lower to upper layers, a skin cell protein called filaggrin breaks down and releases NMF substances, such as PCA. This plays a key role in binding water and helping skin cells adhere properly until it’s time for them to shed and be replaced by new cells.” In layman’s terms, it’s a naturally occurring humectant that’s vital to hydrated, healthy skin.

However, when PCA is found in a skin care product formula, board-certified dermatologist Dr. Dendy Engelman explains that this usually means it’s synthetically made, though it may sometimes be derived from oils and plants. When applied topically in product form — be it a cream, serum, or cleanser — PCA still acts as a humectant, though each of its derivatives brings different benefits to the table.

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The Many Forms Of PCA

PCA can be found on its own in skin care products, but according to Julio Lamberty, cosmetic chemist at Paula’s Choice, it’s more often combined with other active molecules such as mineral salts, amino acids, and fatty alcohols to form multifunctional complexes or derivatives.

The most common derivatives of PCA found in beauty are its mineral salt forms, such as sodium PCA (by far, the most popular), potassium PCA, magnesium PCA, and calcium PCA. While sodium PCA and potassium PCA are great physical moisturizers, Lamberty says that magnesium PCA is also great for combating tired skin while calcium PCA has a restructuring and reparative effect on stressed and mature skin.

Also in the salt PCA family are zinc PCA and copper PCA, both of which regulate sebum, which is why Dr. Engelman says they’re often used to treat excess oil and acne without drying out the skin (because remember, they’re humectants!). Arginine PCA, also a hydrating salt form of PCA, has the ability to both firm and lighten the skin.

With the above in mind, it’s important to do your research before seeking out PCA products. “Different types of PCA target different skin types and concerns, so it’s important to look at what type of PCA is in your skin care in order to make sure you’re receiving the correct treatment,” says Dr. Engelman.

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How To Use PCA

PCA (and the many derivatives under the PCA umbrella) can be found in a pretty wide range of products. “PCA can be found in various hydrating serums, creams, or lotions, and also in cleansers and spray products [like toners and mists] to help retain moisture,” says board-certified dermatologist Dr. Marisa Garshick. She mentions that it can sometimes be found in hair care products, such as shampoos or conditioners, to add additional moisture and shine to the hair and scalp. That said, how and how often you use PCA will vary from product to product, but according to Dr. Engelman, most products containing PCA are generally safe to use daily because it’s not a harsh ingredient.

When it comes to mixing PCA with other ingredients or products, Dr. Garshick says it can be beneficial to pair it with other humectants that help attract and bind moisture to the skin, such as ceramides or hyaluronic acid, or with occlusive ingredients that help trap moisture in, like oils and butters — basically, anything that will help increase its moisture-boosting power. It plays nicely with most ingredients in general, Lamberty pointing out that in addition to ceramides and HA, it’s often formulated with omega fatty acids, amino acids, niacinamide, vitamin C, and retinol.

However, there are a few instances where PCA can react negatively with another ingredient, particularly nitrosating ingredients like diethanolamide. Dr. Garshick mentions that, according to the Cosmetic Ingredient Review database, these ingredients can break down into nitrosamines (known carcinogens) when mixed together. However, this has more to do with these ingredients being combined in the same formula and not something the average consumer needs to worry about when layering products.

Who Is A Good Candidate To Use PCA?

Depending on the particular PCA, anyone with dry skin — as well as anyone with skin conditions that cause dryness and flaking, such as eczema or psoriasis — could benefit from it, while someone with oily skin could benefit from its sebum-regulating forms like zinc and copper PCA. But in general, Dr. Engelman says it’s safe for all skin types and tones: “Since PCA is naturally occurring in the body, most people have no adverse reaction to it, which means that it’s also safe for sensitive skin.”

As Lamberty puts it, if you’re looking to moisturize, improve skin barrier function, and maintain the health and integrity of your skin, consider bringing PCA into the mix. “It meets the fundamental needs of all skin, even the most sensitive,” he says.

Below, seven products that contain PCA’s many forms — from sodium PCA to zinc PCA — to incorporate into your skin care routine.

We only include products that have been independently selected by TZR's editorial team. However, we may receive a portion of sales if you purchase a product through a link in this article.