CosmeticBet
Water-binders

Propylene glycol

INCI: PROPYLENE GLYCOL · also 1,2-Propanediol

A water-holding solvent, and the 2018 Allergen of the Year.

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C3H8O276.09 g/mol
oxygencarbonhydrogen
3D shape from PubChem 1030

How common

All products16%
In hair colours43%
In shampoos25%
In conditioners18%

2,307 of 14,784 products with a full ingredient list in Open Beauty Facts; No. 15 of all the names found on their labels.

What it is

  • A small synthetic alcohol: a clear, colourless, slightly syrupy liquid that absorbs water. In US food the FDA classes it as “generally recognized as safe”.

    3 sourcesHide
    Propylene glycol is a synthetic liquid substance that absorbs water.[1] PubChem (US National Library of Medicine) · open source
    Propylene glycol is clear, colorless, slightly syrupy liquid at room temperature.[1] PubChem (US National Library of Medicine) · open source
    The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is "generally recognized as safe[1] PubChem (US National Library of Medicine) · open source

Why it is in products

  • To hold moisture, to dissolve other ingredients and to make thick formulas runnier.

    2 sourcesHide
    Propylene glycol is an aliphatic alcohol that functions as a skin conditioning agent, viscosity decreasing agent, solvent, and fragrance ingredient in cosmetics.[2] US Cosmetic Ingredient Review expert panel · 2012 · open source
    It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products.[1] PubChem (US National Library of Medicine) · open source

Downsides and safety

  • It can irritate the skin and, more rarely, cause allergy: dermatologists named it Allergen of the Year 2018. Being both a weak allergen and an irritant, it makes patch tests hard to read.

    Good evidence2 sourcesHide
    has been granted the dubious honor of being named the American Contact Dermatitis Society's Allergen of the Year for 2018[3] Study · 2018 · open source
    because it acts as both a weak sensitizer and an irritant, confounding the results of positive patch tests[3] Study · 2018 · open source

  • The US expert panel found no skin allergy at the amounts used, but irritation remained a concern: it concluded it is safe when products are made not to irritate.

    Well established2 sourcesHide
    Clinical studies demonstrated an absence of dermal sensitization at use concentrations, although concerns about irritation remained.[2] US Cosmetic Ingredient Review expert panel · 2012 · open source
    are safe as used in cosmetic formulations when formulated to be nonirritating[2] US Cosmetic Ingredient Review expert panel · 2012 · open source

Where it works

Works insidethe product

Mostly in the product, as a solvent and to hold water.

SourceHide
It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products.[1] PubChem (US National Library of Medicine) · open source

Rules

European Union

  • No EU limit: it is not on the regulation’s lists of banned or restricted substances, preservatives or UV filters.

    How we checkedHide
    We searched Annexes II to VI of the EU regulation (consolidated text of 18 May 2026): no entry.open the list

United States

  • Not on the FDA’s list of prohibited or restricted cosmetic ingredients. In the US, cosmetics and their ingredients (other than colour additives) don’t need FDA approval before sale.

    SourceHide
    Under U.S. law, cosmetic products and ingredients, other than color additives, do not need FDA approval before they go on the market[4] US Food and Drug Administration · open source
    We searched the FDA’s list of prohibited and restricted cosmetic ingredients: no entry.open the list

Sources

  1. PubChem: Propylene glycol (CID 1030), record description PubChem (US National Library of Medicine)PubChem (US National Library of Medicine)
  2. Safety assessment of propylene glycol, tripropylene glycol, and PPGs as used in cosmetics International journal of toxicology, 2012US Cosmetic Ingredient Review expert panel
  3. Propylene Glycol Jacob SE et al., Dermatitis : contact, atopic, occupational, drug, 2018Study
  4. Prohibited & Restricted Ingredients in Cosmetics | FDA US Food and Drug Administration

Checked against these sources on 4 November 2026. Spot a mistake? Tell us.