Tromethamine is a synthetic ingredient that is used in a variety of cosmetics and personal care products as a pH adjuster and a fragrance ingredient.
Tromethamine, also known as tris or THAM, is an organic amine proton acceptor, with substitution at the 2 position. It is frequently used in biochemistry and molecular biology as a component of buffer solutions. Additionally, tromethamine is used in the synthesis of surface-active agents and pharmaceuticals, and also as an emulsifying agent for mineral oil and paraffin wax emulsions, leather dressings, textile specialties, polishes, and cleaning compounds. In the medical field, tromethamine is occasionally used as a drug. It can be administered in intensive care for its properties as a buffer to treat severe metabolic acidosis in specific circumstances. Furthermore, some medications are formulated as the “tromethamine salt”, such as ketorolac tromethamine.
In cosmetics and personal care products, tromethamine functions as a pH adjuster and a fragrance ingredient. According to the United States Food and Drug Administration (FDA) Voluntary Cosmetic Registration Program (VCRP), tromethamine is used in 488 leave-on products and 70 rinse-off products. It was reported to be used up to 3.7% in leave-on nail creams and lotions. Other products include eye makeup up to 2%, fragrance preparations up to 0.2%, and skin care preparations up to 3.1%.
As a pH adjuster, tromethamine is used to establish and hold the pH of a product. In chemistry, pH stands for ‘potential hydrogen’ and it refers to the level of acidity or alkalinity in a given solution. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The useful buffer range for tromethamine is between 7 and 9.
The skin’s normal pH is slightly acidic (typically between 4 and 6). This acidity of the skin is termed the “acid mantle” and is maintained by sebaceous glands, sweat glands, and normal skin flora. The acid mantle provides a film of amino/lactic acids and oils that effectively protect skin from environmental factors (i.e. bacteria, pollutants) that contribute to premature aging and irritation.
The pH of cosmetics and skin care products is important to maintain the skin’s normal pH as closely as possible. On one hand, if a product is too acidic it may irritate the skin or cause a stinging sensation. On the other hand, a product that is too alkaline is detrimental because it depletes your skin of vital, natural fats (or “lipids”). Additionally, a disrupted acid mantle will not allow for products to absorb into the skin as well. This is why pH adjusters like tromethamine are useful in the formulation of cosmetic products.
The safety of tromethamine has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. After reviewing relevant animal and human data related to this ingredient, the Panel concluded that tromethamine is safe in the present practices of use and concentration in cosmetics and personal care products.
According to EWG’s Skin Deep Cosmetic Database, tromethamine is considered to be a low hazard ingredient. The Database does note concerns regarding neurotoxicity and organ system toxicity, which are derived from animal studies that demonstrated brain and nervous system effects at moderate doses. The Database also cites data gaps and a lack of information available regarding tromethamine. However, no other studies were found that suggested negative side effects from topical tromethamine.
References: Wikipedia, “Tris”, Chemists Corner, “The Importance of pH in Cosmetic Formulation”, SebaMed, “Too Acidic, Too Alkaline: The Different Dangers”, 2016, Cosmetic Ingredient Review, “Safety Assessment of Tromethamine, Aminomethyl Propanediol, and Aminoethyl Propanediol as Used in Cosmetics”, 2013, EWG’s Skin Deep Cosmetic Database, “Tromethamine”.