Ingredient dictionary

Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate

A synthetic antioxidant that keeps the oils and fats in a formula from going stale, changing color, or smelling off. It is on the label of 88 products in our library. Checked against our library November 6, 2026.

The catch: none for most people; check the full product list if your skin reacts easily.

What Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate does

Slows oil breakdown from air exposure
Helps keep scent and color stable
Protects the formula over its shelf life

This ingredient is made by chemical synthesis, not taken from plants or animals. It belongs to a type of antioxidant called a hindered phenol, which slows oxidation, the reaction with air that makes oils go off. Its large molecule dissolves in oil rather than water, so it blends into the oily part of a formula.

Formulators add it because oils, butters, and waxes slowly react with air over time. That reaction can cause off smells, yellowing, or a stale feel. A small amount helps the product stay fresh for longer.

Good for

Suits formulas with oils or fats, such as body lotions, deodorants, cleansers, and eye makeup, where air can affect those oils over time.

Be careful if

Nothing in particular for most skin types.

Frequently asked questions

Is Pentaerythrityl Tetra-Di-T-Butyl Hydroxyhydrocinnamate safe to use?

It is widely used in cosmetics and is generally well tolerated. As with any ingredient, a few people may react to it. If your skin is sensitive, try a small test patch first.

Why is it in mascara and eyeliner?

Oils and waxes in mascara and eyeliner can slowly change over time. The antioxidant helps the formula keep its color, texture, and scent for longer. It protects the product itself, not your lashes.