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Citric Acid

Citric acid

Well toleratedpH adjusterph-adjusterbufferchelatorexfoliant

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

Also written as: 2-Hydroxypropane-1,2,3-tricarboxylic acid

What it is

Citric acid is a weak organic acid that occurs naturally in citrus fruit, but the cosmetic grade is made industrially by fermenting sugars with the mould Aspergillus niger. In most face masks it is present at well under 1% purely to pull the pH down into a skin-friendly range, often paired with sodium citrate as a buffer. It also binds trace metals, so it quietly supports formula stability. Only at much higher concentrations, and at a low pH, does it behave as an alpha hydroxy acid (AHA) that loosens dead surface cells.

What it does well

  • Sets and holds the pH so the rest of the formula works properly

    Preservatives, acids and many actives only perform in a defined pH window, and healthy skin sits at roughly pH 4.5-5.5. Citric acid is the most common way to reach that window, which is why it appears in a very large share of masks.

    Strong evidence

  • At AHA-level concentrations it can improve sun-damaged skin

    A controlled study of topical citric acid on photodamaged skin found increased viable epidermal thickness and more glycosaminoglycans, comparable to other alpha hydroxy acids. This applies to deliberate AHA formulas, not to the trace amounts used for pH adjustment.

    Moderate evidence

Worth knowing

  • Can sting on broken or very sensitive skin

    Any acid at low pH can produce transient stinging on compromised skin, and this rises with concentration. At the fractional percentages used for pH adjustment, stinging is uncommon; in a deliberate AHA mask it is more likely.

Where the EU stands

No specific restriction

Not restricted for cosmetic use in the EU. It appears in no Annex of the Cosmetics Regulation, though finished AHA products must still be safe at their in-use pH.

Sources (2)

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

  1. [1]
    Citric acid increases viable epidermal thickness and glycosaminoglycan content of sun-damaged skin

    Dermatologic Surgery · 1997 · doi:10.1111/j.1524-4725.1997.tb00391.x

    Topical citric acid produced measurable increases in viable epidermal thickness and dermal glycosaminoglycans in photodamaged skin, comparable with other alpha hydroxy acids.

  2. [2]
    Skin pH: from basic science to basic skin care

    Acta Dermato-Venereologica · 2013 · doi:10.2340/00015555-1531

    Skin's naturally acidic surface pH is central to barrier repair, stratum corneum integrity and antimicrobial defence, which is the reason products are deliberately pH-adjusted rather than left alkaline.

Masks that contain Citric Acid