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Tromethamine

TRIS

Well toleratedpH adjusterph-adjusterbufferneutraliser

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

Also written as: TRIS · Trometamol · Tris(hydroxymethyl)aminomethane · Triethanolamine substitute

What it is

Tromethamine is a small amine that acts as a gentle alkali and buffer; the same compound is used as a buffering agent in medicines. In cosmetics it neutralises carbomer and other acidic polymers and holds pH steady, and it is frequently chosen instead of triethanolamine. That substitution does not close the nitrosamine question: the CIR Expert Panel's final report cautions that products containing tromethamine could form nitrosamines and that formulators should continue to avoid their formation.

What it does well

  • Neutralises acidic thickeners and buffers pH gently

    As a weak base it is easier to control than sodium hydroxide and holds pH within a narrow range, which suits gels containing acidic actives.

    Strong evidence

Worth knowing

  • Isolated reports of contact allergy

    Contact allergy to tromethamine has been described occasionally in dermatology practice, mainly with medicated topicals used long-term. It is not a common sensitiser at cosmetic use levels.

    Matters most toPeople with known amine or excipient allergies confirmed by patch testing.

Where the EU stands

No specific restriction

Tromethamine is not named in any Annex of the Cosmetics Regulation, so no limit applies to it by name. Annex III entry 61 does restrict monoalkylamines, monoalkanolamines and their salts as a class: minimum purity 99%, maximum secondary amine content 0.5% in the raw material, maximum nitrosamine content 50 micrograms per kg, not to be used with nitrosating systems, and kept in nitrite-free containers. No EU text says in terms that tromethamine falls in that class, but the cosmetic-grade material reported to the CIR Expert Panel meets all three of those figures.

Regulation (EC) No 1223/2009 - no annex entry for tromethamine; Annex III entry 61 restricts monoalkylamines, monoalkanolamines and their salts as a class · source ↗

Sources (2)

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

  1. [1]
    Safety Assessment of Tromethamine, Aminomethyl Propanediol, and Aminoethyl Propanediol as Used in Cosmetics (Final Report)

    Cosmetic Ingredient Review Expert Panel · 2013

    A manufacturer reported cosmetic-grade tromethamine at 99% purity, with secondary amines at a maximum of 0.5% by weight and nitrosamines at 50 ppb, below the level of detection. The Panel found the ingredient safe in the present practices of use and concentration, but cautions that products containing it could form nitrosamines and that formulators should continue to avoid their formation.

  2. [2]
    Safety Assessment of Tromethamine, Aminomethyl Propanediol, and Aminoethyl Propanediol as Used in Cosmetics

    International Journal of Toxicology (Cosmetic Ingredient Review) · 2018 · doi:10.1177/1091581817738242

    The peer-reviewed form of the same assessment. All three ingredients are reported to function as pH adjusters, and the Panel concluded they are safe in cosmetics in the practices of use and concentration given in the assessment.

Masks that contain Tromethamine