Skim through

What it does: cleansing, emulsifying, surfactant

The science

Ceteareth-20 is a common functional ingredient that helps to keep the oil-loving and water-loving ingredients together (emulsifier), and stabilizes and thickens products. It also helps other active ingredients to dissolve in the solvent.

Chemically speaking, it is ethoxylated Cetearyl Alcohol, meaning that some ethylene oxide is added to the fatty alcohol to increase the water-soluble part in the molecule. The result is that the mainly oil soluble, emollient fatty alcohol is converted to an emulsifier molecule that keeps oil and water mixed in creams.

The number in the name of Ceteareth emulsifiers refers to the average number of ethylene oxide molecules added and 20 makes a good emulsifier.

Benefits for your hair

Promotes hydration

Ceteareth-20, as an emollient, helps to add moisture to the hair. It is hydrophilic in nature, thereby attracting water molecules and helping to retain moisture, keeping your strands well hydrated.

Promotes softness and helps detangle

As it is hydrating, ceteareth-20 helps to make the hair softer, silkier, and shinier, which in turn, makes the hair easier to detangle.

Prevents dry and itchy scalp

Another benefit of the added hydration, ceteareth-20 helps to improve scalp health by reducing dryness and itchiness.

TLDR 

Ceteareth-20 helps stabalize and thicken products. It improves scalp health by reducing dryness and itchiness, and moisturizes and softens the hair, making it easier to detangle.