PCA is an organic compound known as pyroglutamic acid. It actually stands for pyrrolidine carboxylic acid. Other names for this skincare ingredient include L-polyglutamic acid, 2-Pyrrolidone-5-Carboxylic Acid, and 5-Oxo-L-Proline (1).
Sodium PCA is the sodium salt of PCA. This is a substance that is recommended to be used in concentrations of less than 5%. Concentrations greater than 5% can lead to reddening of the skin, or skin erythema (1).
One clinical study of topical application of sodium PCA to male volunteers showed skin irritation in a few volunteers above 6.25% concentration (1).
Sodium PCA is present in a variety of skincare products and other cosmetics. It is found in moisturizers, face masks, hair conditioners, and makeup removers. When used in the correct concentrations in cosmetics, it is a humectant (1). Humectants are substances that are able to hold onto water in the skin. They attract water molecules and retain this water to help regulate the balance of water content in the skin. This ingredient has a conditioning effect on skin and hair.
Clinical tests have shown sodium PCA to be non-irritating when applied topically. In addition, it has been deemed safe to use in cosmetic formulations (1).
One downfall of sodium PCA is that it does not penetrate the skin completely. When applied topically, it does yield some effect on the skin, but it is not able to be absorbed as efficiently as some other cosmetic ingredients.
PCA is present in human plasma and is also found in the epidermis (1). It makes up part of the “Natural Moisturizing Factors” (NMF) of the skin. This is made up of a variety of proteins and other molecules that contribute to the structure and integrity of the skin barrier, keeping your skin healthy and functioning properly.
Hyaluronic acid (HA) is a molecule that has the ability to retain water in the skin. Like sodium PCA, it functions as a skin humectant. In addition, research has pointed to a multitude of benefits of using HA topically.
One main contributor to aging involves the loss of moisture in the skin. This dryness upsets the skin’s moisture barrier, causing wrinkling of the skin. Extrinsic factors of aging include UV rays from the sun, which damage the skin’s DNA and degrades collagen production.
The extracellular matrix (ECM) is a network of proteins and other molecules that give structure to cells. HA is present in the ECM and works to maintain moisture levels in the skin. 50% of hyaluronic acid in the body is found in the skin (2).
The synthesis of HA has been shown to be increased during wound healing. HA also regulates water content and stabilizes structures in the skin. When exposed to UV radiation, HA is immediately increased in the skin within minutes (2).
HA-based creams and gels have anti-aging and anti-wrinkle properties (3). This “aging” refers to the look of dry, wrinkled, dehydrated skin. It includes skin that is dull-looking and perhaps irritated or red. Use of HA rejuvenates the look of skin when applied (3).
In addition, it stimulates collagen and elastin production in the skin. In order to achieve these exciting benefits, HA works to increase skin hydration, skin tightness, and lessen the overall look of pigmentation of the skin.
HA Sizes Affect Skin Penetration
The size of the HA molecule also matters. Depending on the size, HA penetrates more or less into the skin. Smaller size HA molecules penetrate deeply into the skin, providing deep hydration (4). Larger HA molecules sit atop the skin, providing surface hydration. However, larger HA molecules can also hold onto more water/moisture since it has a larger surface area. Your best bet is to find a product that contains HA in multiple sizes.