CosmeticBet
Helpers (pH, solvents)

Water

INCI: AQUA · also Water

Usually the main ingredient, and the reason products need preserving.

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H2O18.02 g/mol
oxygenhydrogen
3D shape from PubChem 962

How common

All products72%
In shower gels97%
In body lotions90%
In face moisturisers90%

10,715 of 14,784 products with a full ingredient list in Open Beauty Facts; No. 1 of all the names found on their labels.

What it is

  • Water: one oxygen atom bonded to two hydrogen atoms. On EU labels it is called “aqua”.

    3 sourcesHide
    Water is an oxygen hydride consisting of an oxygen atom that is covalently bonded to two hydrogen atoms.[1] PubChem (US National Library of Medicine) · open source
    aqua[2] PubChem (US National Library of Medicine) · open source
    2344 AQUA[3] EU law · 2022 · open source

Why it is in products

  • It is usually the main ingredient of a cosmetic, and it is the most widely used solvent.

    2 sourcesHide
    Usually, water is the major constituent of cosmetics[4] Study · 2018 · open source
    the most widely used solvent[1] PubChem (US National Library of Medicine) · open source

Downsides and safety

  • Germs grow in water, so products with water need protecting: with preservatives, or with ingredients that hold on to water and leave less of it for germs.

    Good evidence2 sourcesHide
    but it is an ideal growth factor for microorganisms[4] Study · 2018 · open source
    To solve this problem, certain substances can reduce the water activity (aw)[4] Study · 2018 · open source

Where it works

Works insidethe product

In the product, as its base.

SourceHide
Usually, water is the major constituent of cosmetics[4] Study · 2018 · open source

Rules

European Union

  • Ingredient lists must use the names of the EU’s glossary, which follows the international INCI names; there, water is “aqua”.

    3 sourcesHide
    The ingredients are to be expressed using the common ingredient names set out in a glossary[3] EU law · 2022 · open source
    The glossary is required to take account of internationally recognised nomenclatures including the International Nomenclature of Cosmetic Ingredients (INCI).[3] EU law · 2022 · open source
    2344 AQUA[3] EU law · 2022 · open source

Sources

  1. PubChem: Water (CID 962), record description PubChem (US National Library of Medicine)PubChem (US National Library of Medicine)
  2. PubChem: Water (CID 962), depositor-supplied synonyms PubChem (US National Library of Medicine)PubChem (US National Library of Medicine)
  3. Commission Implementing Decision (EU) 2022/677 on the glossary of common ingredient names for the labelling of cosmetic products Publications Office of the European Union (EUR-Lex/Cellar), 2022EU law
  4. Cosmetics Preservation: A Review on Present Strategies Molecules : A Journal of Synthetic Chemistry and Natural Product Chemistry, 2018Study

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