Glycerin
The most common humectant in hair care. It draws water into the hair and holds it there, so curls feel softer and more defined — but its effect changes with the humidity.
About Glycerin
Glycerin is a simple, clear, slightly sweet liquid made from plant oils or as a by-product of soap and biodiesel production. It is a humectant: its molecules attract and hold water. That is why it appears in so many leave-ins, curl creams, gels and conditioners for curly and coily hair.
On the hair, glycerin helps strands hold onto water from the product and from the air, which makes them feel softer, more flexible and less brittle, and helps curls clump together. It also helps other ingredients spread and gives formulas a cushiony feel.
The catch is that glycerin works with the weather. When the air is humid — a high dew point, roughly above 60 °F — glycerin keeps pulling moisture in, and hair can swell and frizz. When the air is very dry — a low dew point, roughly below 35 °F — there is little water to attract, and some people find glycerin-heavy products leave their hair feeling dry or sticky. In between, it is usually ideal. If your twist-out frizzes on muggy days, check how high glycerin sits on your product labels.
Glycerin is approved for the Curly Girl Method and suits most hair types; people with low porosity hair often like light humectants because they don't sit on the surface like butters. The Cosmetic Ingredient Review panel has assessed glycerin as safe as used in cosmetics.
How our checker rates it
| Mode | Rating | Why |
|---|---|---|
| Curly Girl | OK | No concerns for this mode. |
| Relaxed hair | OK | No concerns for this mode. |
| Low porosity | Good | Humectant — draws water in. Low-porosity hair usually does well with humectant-rich products. |
| Protein-sensitive | OK | No concerns for this mode. |
Ratings assume it is listed near the top of the label. After the first preservative or fragrance (likely 1% or less) most cautions soften.
What humectant ingredients do
Ingredients that attract and hold water. How well they work depends on air moisture (dew point) and your porosity.
Also listed as
- glycerol
- glycerine
- vegetable glycerin
- vegetable glycerine
Similar ingredients
Sources
Last data update:
- Robbins CR. Chemical and Physical Behavior of Human Hair. 5th ed. Springer; 2012. Reference text on hair structure, surfactants, conditioning agents, protein, heat and chemical treatments.
- Cosmetic Ingredient Review (CIR). Ingredient safety assessments. Safety assessments for cosmetic ingredients cited on ingredient pages.
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