A semi-essential amino acid meaning that enough has to be eaten from it so that the body does not use up essential amino acids (that our body cannot produce itself) to synthesize it. It has an important role in regulating the immune defense, allergic reactions, and inflammatory processes in the body.

As for skincare, it's a skin moisturizer that might also protect from some skin infections.

https://incidecoder.com/ingredients/histidine