Glycerin: the story of the most familiar moisturizer
Arin Editorial · how this is made
You see 'glycerin' on the label. It sounds like a lab product. It is a clear, syrupy liquid that mixes with water and alcohol, and it is one of the building blocks of animal and plant fats.
What is it?
Glycerin (glycerol in chemistry texts) is an alcohol with three hydroxyl groups. It occurs naturally in animal and plant fats as glycerides, and in intracellular spaces as lipids. It can be plant-derived, animal-derived, or synthetic; the molecule is the same. It is a clear, syrupy liquid that can crystallize at low temperatures.
What does it do in cosmetics?
Glycerin is a humectant, meaning it draws water into the upper layers of the skin, supports the natural moisturizing factor, and helps maintain the skin barrier. It is one of the most studied moisturizers and is also used in hair care. Its comedogenic rating is 0/5 and its irritation score is 0/5, so it won't clog pores and is generally considered suitable for nearly every skin type. It appears in about 99% of moisturizers.
What do safety reviews say?
The Cosmetic Ingredient Review (CIR) panel concluded in 2014 that glycerin is safe in the current uses and concentrations in cosmetics. Its acute toxicity is low; fatal effects require very large doses. Long-term animal studies found no increase in tumors. Individual genotoxicity records are mixed, but the overall assessment raised no concern. Estrogen receptor screens found no activity.
Source matters less than purity
Industrial documents call it glycerol; cosmetic labels usually say glycerin. It is the same molecule. There is one supply-chain issue to watch: in 2007 the FDA advised pharmaceutical manufacturers to test all glycerol batches for diethylene glycol contamination. That is a quality issue, not a problem with glycerin itself.
The CIR panel found glycerin safe as used in cosmetics in 2014, and the FDA advised testing glycerol supplies for diethylene glycol contamination in 2007.
Seeing glycerin on a label requires no special action. It doesn't clog pores and has a low irritation profile. If a product stings or turns red on your skin, stop using it; that is usually caused by another ingredient in the formula. Glycerin is generally well tolerated, even on dry or sensitive skin.