PCA is a chemical compound, (2-Pyrrolidone-5-Carboxylic Acid), known as pyroglutamic acid is an internal amide of L-glutamic acid found in fruit, vegetables, herbs and molasses. It is produced from l-glutamic acid by an autoclave that heats water to 140°C.

What it is used for and where
Cosmetics
Skin conditioning agent - Humectant. Humectants are hygroscopic substances used to minimise water loss in the skin and to prevent it from drying out by facilitating faster and greater absorption of water into the stratum corneum of the epidermis. The epidermis is the most superficial of the three layers that make up the human skin (epidermis, dermis and hypodermis) and is the layer that maintains hydration in all three layers. In turn, the epidermis is composed of five layers: corneum, the most superficial, lucidum, granulosum, spinosum and basale. Humectants have the ability to retain in the stratum corneum the water they attract from the air and have the function of moisturising the skin. It is better to use them before emollients that are oil-based.

Skin conditioning agent - Miscellaneous. This ingredient has the task of modifying the condition of the skin when it is damaged or dry by reducing its flakiness and restoring its elasticity.
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CAS: 149-87-1, DL- 98-79-3