Histidine HCl

We confirmed this ingredient's definition and its registered function in public regulatory databases, but found no published study data on how the ingredient itself acts on the skin (checked by KAIAN, September 2026). We will update this page if new reports appear.

The hydrochloride salt of histidine, an amino acid that makes up the stratum corneum's natural moisturizing factor (NMF). Formulated to moisturize and condition the skin

In in vivo measurements of human stratum corneum (confocal Raman spectroscopy), histidine is reported as one of the major constituents of NMF. In the stratum corneum it is the precursor of urocanic acid (a stratum corneum component). A double-blind human study applying a mixture of NMF components including histidine for 14 days has been reported, but the topical effect of histidine (hydrochloride) alone was not confirmed (uptake of histidine into isolated corneocytes has been reported in vitro)

No public data on typical concentrations in cosmetics could be confirmed (varies by product)

No public data on the time to a perceptible effect with topical use could be confirmed

Ingredient-specific irritation data not confirmed. The US CIR Expert Panel concluded that α-amino acids are safe as cosmetic ingredients under the practices of use and concentration assessed (2013; whether this ingredient was among those assessed is unconfirmed)