Propylene Glycol
A light humectant and solvent that helps hair hold moisture and helps other ingredients dissolve and spread. Not a drying alcohol.
About Propylene Glycol
Propylene glycol is a small, clear, odorless liquid that belongs to the glycol family. In hair products it does two things: it acts as a humectant, helping hair attract and hold water, and it works as a solvent that keeps extracts, fragrance and preservatives evenly dissolved. It also helps products spread easily and can improve how well other ingredients reach the hair and scalp.
Compared with glycerin it feels lighter and less sticky, which is why it often appears in leave-ins, sprays and scalp products. Like other humectants, its moisturizing effect depends somewhat on the humidity around you.
Despite the 'glycol' name and its chemical relationship to alcohols, propylene glycol is not a drying alcohol and is approved for the Curly Girl Method. People with low porosity hair often do well with light humectants like this one because they don't coat the surface.
On safety, the Cosmetic Ingredient Review panel has reviewed propylene glycol and considers it safe as used in cosmetics. A small number of people develop contact irritation or allergy to it, which usually shows up as itching or redness on the scalp or hairline. If you notice that after starting a new product, stop using it and see whether propylene glycol is the common ingredient.
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
- 1,2-propanediol
- propane-1,2-diol
- pg
Similar ingredients
Sources
Last data update:
- Cosmetic Ingredient Review (CIR). Ingredient safety assessments. Safety assessments for cosmetic ingredients cited on ingredient pages.
- 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.
How we research and update pages: editorial policy. Spotted an error? Tell us.