Skim through

What it does: moisturizer, humectant, skin-identical ingredient 

Also called: sodium pyrrolidone carboxylic acid

The science

PCA stands for Pyrrolidone Carboxylic Acid and can be found naturally in our skin. The sodium salt form of PCA is an important skin-identical ingredient and great natural moisturizer that helps the skin to hold onto water and stay nicely hydrated. 

Benefits for your hair

Prevents dryness

It helps to retain the moisture in your strands, thereby keeping the hair hydrated and nourished.

TLDR 

Sodium PCA is a skin-identical ingredient which helps to moisturize hair and prevent dryness.