What it is
Tromethamine is an organic compound with the formula (HOCH2)3CNH2, also known as Tris or trometamol. It is a weak base whose conjugate acid has a pKa of about 8.07 at 25 degrees Celsius, which makes it an effective buffer for maintaining a roughly neutral to slightly alkaline pH. In cosmetic formulas it functions as a pH adjuster and buffering agent, and it is frequently used to neutralize carbomer-type thickeners so they swell and gel. Outside cosmetics it is widely used as a buffer in biochemistry and as a medical agent.
Safety & warnings
Tromethamine is used in small amounts to fine-tune a formula's pH, so user-facing exposure is low. Because its main job is to bring acidic ingredients such as carbomer to a skin-comfortable pH, properly formulated products are balanced rather than harshly alkaline. It is a long-established buffering ingredient used across cosmetics and pharmaceuticals.
Origin & sourcing
Tromethamine is a synthetic small molecule manufactured for laboratory, pharmaceutical, and cosmetic use. It is supplied as a defined chemical compound rather than extracted from a natural source.
History
Tris(hydroxymethyl)aminomethane is extensively used in biochemistry and molecular biology as a component of buffer solutions, particularly in work involving nucleic acids, and in medicine it serves as an alternative to sodium bicarbonate for treating severe metabolic acidosis. Its value as a buffer comes from its pKa near physiological pH, although that pKa is notably temperature dependent.
Questions everyone asks
What does tromethamine do in skincare?
It adjusts and buffers the pH of a formula and is often used to neutralize carbomer so the product can thicken into a gel.
Is tromethamine an active ingredient?
No. In cosmetics it is a formulation aid that controls pH; it does not provide sun protection or a direct skin benefit on its own.
Is tromethamine the same as Tris?
Yes. Tris, trometamol, and THAM are common names for tromethamine, tris(hydroxymethyl)aminomethane.