Skim through

What it does: emollient, emulsifying, emulsion stabilising, foam boosting, masking, opacifying, surfactant/cleansing, viscosity controlling

The science

Stearyl Alcohol is a handy multi-tasker. It is a white to light yellowish oil-loving wax that works very well in oil-in-water emulsions. It makes the hair feel nice and smooth (emollient), stabilizes oil-water mixes and gives body (volume) to them.

It's a so-called fatty alcohol - the good, emollient type of alcohol that is non-drying and non-irritating. It is often mixed with another fatty alcohol, Cetyl Alcohol, and the mixture is called Cetearyl Alcohol.

Benefits for your hair

Protects hair

Stearyl Alcohol is opacifying, meaning it makes the formula more opaque, thus protecting hair from sunlight. 

Promotes hydration and softness

This ingredient, as an emollient, provides moisture to the hair and makes it softer and smoother.  

Promotes detangling and reduces frizz

As it is hydrating, Stearyl Alcohol helps to make the hair easier to detangle and reduces frizz. 

TLDR 

Stearyl Alcohol stabalizes formulas, making it easier to spread them. It protects hair from the sun while promoting hydration and softness, reducing frizz, and making it easier to detangle hair.