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Sulfuric Acid

INCI: SULFURIC ACID

Reviewed by Rosie · Last updated 14 Aug 2026

A pH buffer used to stabilise skincare formulations

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What Is Sulfuric Acid?

Sulfuric acid is a strong inorganic acid commonly used in cosmetic formulations as a buffering agent. In skincare products, it functions to maintain stable pH levels, helping formulators achieve the desired acidity or alkalinity of a product without significantly altering other ingredients.

As a buffer, sulfuric acid works alongside other components to resist pH changes that might occur during storage or use. This role is primarily technical rather than therapeutic—it exists to keep a formula stable and effective, rather than to deliver direct skin benefits.

How It Works

Sulfuric acid acts as a buffer by donating or accepting hydrogen ions (H+) depending on the pH of the surrounding environment. When a formula becomes too alkaline, sulfuric acid releases H+ ions to lower pH; when it becomes too acidic, it can work in concert with other buffering components to resist further acidification. This stabilising action helps maintain the target pH range that was established during product development.

Clinical Evidence & References

Limited direct clinical evidence exists for sulfuric acid's skincare benefits because its function is primarily technical. No robust studies examine topical sulfuric acid application for skin concerns. Its use is governed by cosmetic regulatory bodies such as the European Commission and FDA, which restrict concentrations to levels considered safe for topical use.

Evidence of safety comes largely from decades of formulation history and regulatory oversight rather than from dedicated clinical trials of the ingredient itself.

How to Use

Sulfuric acid is used by formulators, not end consumers. When present in finished skincare products at approved concentrations, it requires no special application instructions. Use your product as directed on the label.

Safety & Precautions

Sulfuric acid is approved for use in cosmetics at regulated concentrations and is generally well-tolerated when present in finished skincare products. However, undiluted or highly concentrated sulfuric acid is caustic; cosmetic formulations are strictly controlled to prevent harm.

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