What it is
Tannic acid is a hydrolyzable tannin built from gallic acid units esterified to a glucose core, giving it strong polyphenolic antioxidant and astringent properties. In cosmetic formulas it is included at low levels to help neutralize free radicals and impart a temporary tightening or toning feel to the skin. Its phenolic groups can also bind metal ions and proteins, which contributes to its astringent character.
Safety & warnings
Tannic acid is generally well tolerated at the low concentrations used in cosmetics. Because it is a polyphenol that can bind proteins, very high levels can feel drying or tightening on the skin, and as a plant-derived material it carries a low potential for sensitization in susceptible individuals.
Origin & sourcing
Naturally derived; it is extracted from plant sources rich in tannins, such as galls (nutgalls) formed on oak and sumac, and from various tree barks and seed pods.
Questions everyone asks
What does tannic acid do in a sunscreen?
It acts mainly as an antioxidant and astringent, helping to scavenge free radicals and impart a light toning feel rather than providing UV protection itself.
Is tannic acid a UV filter?
No. It is an antioxidant and astringent ingredient and is not classified or used as a UV filter.