Sodium Sesquicarbonate

What is Sodium Sesquicarbonate?

Sodium sesquicarbonate is a crystalline, hydrated double salt formed from sodium carbonate and sodium bicarbonate, with the chemical formula Na2CO3·NaHCO3·2H2O. It occurs naturally in mineral deposits like trona or is produced synthetically through controlled reactions. In cosmetics, it appears mainly in rinse-off products such as shampoos, soaps, bath additives, and cleansers. It functions by releasing ions that neutralize acids or bases to adjust pH precisely, stabilizing formulas against environmental shifts. As a buffer, it resists pH fluctuations during use or storage. It also contributes bulk to increase product volume and improve texture, while aiding cleansing through mild effervescence that helps dislodge surface debris when combined with water.

Comedogenic Rating 0/5 Low risk of clogging pores

EWG Safety Rating 1 View on EWG →

PubChem View on PubChem →

Roles in Formulation

This ingredient serves the following purposes in cosmetic formulations:

PH adjuster

Raises or lowers pH to the target range, supporting ingredient performance, preservative efficacy, stability, and user comfort.

Buffering agent

Maintains the pH stability of a formulation.

Bulking agent

Increases mass/volume to build structure and improve handling, commonly used to adjust feel, spread, and cost-in-use without acting as a primary active.

Cleansing agent

Removes dirt, oil, and impurities by lowering surface tension and forming micelles, enabling soils to be lifted and rinsed away from skin, hair, or teeth.

Benefits

Supports stable pH levels to enhance formula performance and skin feel.

Provides gentle cleansing action to remove everyday residues.

Adds volume for improved product consistency and application.

Who It's For

A quick guide for who this ingredient may suit (and who should be cautious).

Who May Benefit	Who Should Avoid
Users of daily cleansers seeking balanced formulations.	Those with known sensitivity to carbonate salts.
Individuals preferring simple, mineral-derived ingredients.	People experiencing dryness from alkaline ingredients.
People incorporating bath or shower products for routine care.	Individuals preferring anhydrous or purely botanical formulas.

Safety Notes

Rated low hazard by safety assessments for cosmetic use.
Typically non-comedogenic and suitable for most skin types.

Frequently Asked Questions about Sodium Sesquicarbonate

What is sodium sesquicarbonate used for in cosmetics?

Primarily for pH adjustment, buffering stability, bulking volume, and supporting cleansing in products like shampoos and soaps.

Is it safe for sensitive skin?

Generally low irritation potential at typical cosmetic concentrations, per safety reviews.

Does it clog pores?

Assigned a comedogenic rating of 0, indicating low likelihood of pore blockage.