Citric Acid

Citric acid is an organic acid found naturally in citrus fruits, for example. In cosmetic products, it is listed under the INCI name Citric Acid. Although consumers often associate it primarily with fruit acids and exfoliation, its main role in many formulations is technical – it is used to precisely adjust and stabilise pH.

The right pH is important for product stability, the effectiveness of the preservative system, the solubility of active ingredients and how well the skin tolerates the product. A formula may contain only a very small amount of citric acid to lower the pH to the desired level. In this case, it cannot automatically be considered an exfoliating active ingredient.

The Cosmetic Ingredient Review safety assessment states that citric acid is used in cosmetics as a pH adjuster, a chelating agent and, in some cases, a fragrance ingredient. After reviewing the available data, the panel concluded that citric acid and the citrates assessed are safe under current conditions of use and at current concentrations in cosmetics.

At higher concentrations and an appropriately adjusted acidic pH, citric acid can act as an alpha-hydroxy acid. It helps loosen the bonds between dead cells on the skin's surface, which may promote a smoother, brighter and more even appearance. However, its effect always depends on the concentration, final pH, product type, contact time with the skin and the formulation as a whole.

In a clinical study, a body lotion containing 20 % citric acid was applied to sun-damaged skin for three months. Biopsies showed an increase in the thickness of the viable epidermis and in the skin's glycosaminoglycan content. However, this was a highly concentrated experimental formulation, so these findings cannot be applied to products in which citric acid is used only to adjust pH.

At exfoliating concentrations, citric acid may cause stinging, redness or irritation, particularly on sensitive or compromised skin. Products with an exfoliating effect should therefore be introduced gradually and used alongside broad-spectrum SPF protection during the day.