Encyclopedia · humectant
Panthenol
A small vitamin B5 alcohol that enters the hair cortex and raised break stress in a lab study; the only humectant here with real hair-fibre data.
What it is
The alcohol form of pantothenic acid, converted to vitamin B5 in living skin. It is common in shampoos, conditioners and leave-ins at low percentages, and is a cosmetic ingredient.
How it works
Imaging of labelled panthenol showed it entering cortical protein regions. Solid-state NMR indicated that it interacts with aromatic protein side chains, and treated hair had higher break stress and stiffness, probably through hydrogen bonds. Marsh 2026
What the studies show
- Panthenol penetrated the cortex, hydrogen-bonded to proteins and raised break stress and elastic modulus on cut hair (Procter & Gamble study). Marsh 2026
- This is a single industry paper, so replication outside the manufacturer is missing.
How it's used in studies
It was studied on cut hair. See the paper for concentrations.
Side effects and safety
Generally well tolerated. A case report of contact urticaria from panthenol in a conditioner exists, and it is rare.
Bottom line
A sensible ingredient to see in conditioners for dry or damaged hair. The benefit is modest tensile support, not repair. We are only moderately sure, as it rests on one industry paper. See humectants and humidity.
Studies 1
Marsh JM et al. Strengthening benefits of panthenol for hair: mechanistic evidence from advanced spectroscopic techniques. Int J Cosmet Sci. 2026
Result: Labelled panthenol penetrated into cortical protein regions and raised break stress and elastic modulus, probably through hydrogen bonding.
Read the study ↗Related
- GlycerinA cheap water-binding ingredient in nearly every conditioner; no peer-reviewed hair study tests it, and the popular humidity rules are untested.
- Hydrolyzed keratinKeratin fragments, usually from wool or feathers, that coat damaged hair and in lab tests partly entered it and raised wet strength; the evidence is small and industry-linked.
- Humectants and humidityHair swells and softens with humidity, but the popular rules about glycerin and humidity have not been tested; panthenol is the humectant with the best fibre data.