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Water

Water

Well toleratedSolventsolventcarrier

No meaningful concern for most people; irritation is possible but rare.

Also written as: Aqua · Eau · Purified Water · Aqua/Water/Eau

What it is

Water is the liquid that most cosmetics are built on, and in a sheet mask it is usually the single largest ingredient by weight. Cosmetic manufacturers do not use tap water: it is purified (typically by reverse osmosis, deionisation or distillation) and tested for microbial contamination before use. Formulators need it because most humectants, salts, acids and many botanical extracts will only dissolve in water.

What it does well

  • Dissolves and delivers the rest of the formula

    Water is the solvent in which humectants, buffers, salts and water-soluble actives are dispersed. Without it, an essence or gel mask could not exist in that form.

    Strong evidence

  • Supplies the water that a mask's occlusive layer then holds against the skin

    The short-term plumping effect of a sheet mask comes largely from hydrating the outer skin layer under an occlusive backing. The effect is real but temporary unless the formula also contains humectants and a barrier-supporting lipid or film.

    Moderate evidence

Worth knowing

  • Water alone does not moisturise for long

    Water applied without humectants or occlusives evaporates within minutes and can leave skin feeling tighter than before. This is a limitation of very simple, watery formulas rather than a safety problem.

    Matters most toPeople with dry skin choosing a mask that is essentially water plus a preservative.

  • Water-based products need effective preservation

    Any product containing water can support bacterial and mould growth, which is why water-based masks always contain a preservative system. This is a normal and necessary part of the formula, not a flaw.

    Matters most toAnyone tempted by 'preservative-free' water-based products, or by decanting masks into other containers.

  • Hard tap water and eczema

    Living in a hard-water area is associated with a higher risk of atopic dermatitis, and laboratory work shows hard water increases how much surfactant is left on the skin after washing. However, a large randomised trial found that installing a domestic water softener produced no meaningful improvement in children's eczema, so the practical importance is limited. This concerns the water you wash in, not the purified water inside a mask.

    Matters most toPeople with eczema in hard-water areas, mainly regarding washing habits.

Where the EU stands

No specific restriction

Water is not listed in any restrictive annex of the EU Cosmetics Regulation. Its quality is instead controlled through the general safety obligation and good manufacturing practice, which require finished products to be microbiologically safe.

Sources (2)

Every link goes to the original: a journal, a PubMed record or an EU document.

  1. [1]
    The Effect of Water Hardness on Surfactant Deposition after Washing and Subsequent Skin Irritation in Atopic Dermatitis Patients and Healthy Control Subjects

    Journal of Investigative Dermatology · 2018 · doi:10.1016/j.jid.2017.08.037

    Hard water left more surfactant on the skin after washing and increased barrier disruption, giving a plausible mechanism for the observed link between hard water and eczema.

  2. [2]
    A randomised controlled trial of ion-exchange water softeners for the treatment of eczema in children

    PLoS Medicine · 2011 · doi:10.1371/journal.pmed.1000395

    Installing a domestic water softener produced no clinically meaningful benefit over usual care for childhood eczema, tempering the practical significance of the hard-water association.

Masks that contain Water