Glossary
A weak organic acid naturally found in citrus fruits, used in skincare as a pH adjuster, mild exfoliant, antioxidant, and preservative system enhancer. At higher concentrations, citric acid functions as an alpha hydroxy acid (AHA) that can brighten skin and improve texture.
Citric acid wears several hats in cosmetic formulations. Its most common role is as a pH adjuster, bringing products into the mildly acidic range (pH 4.5 to 5.5) that matches the skin's natural acid mantle. At these low concentrations, it has no exfoliating effect but ensures the product is compatible with healthy skin.
At higher concentrations (10 to 20 percent), citric acid acts as an AHA exfoliant that dissolves the bonds between dead skin cells, promoting cell turnover and revealing brighter, smoother skin underneath. It also chelates (binds to) metal ions that can catalyze product degradation, extending shelf life.
While citric acid occurs naturally in lemons, oranges, and other citrus fruits, the vast majority of citric acid used commercially is produced through microbial fermentation of sugar by the mold Aspergillus niger. This biofermented citric acid is chemically identical to the natural form but is produced at far greater scale.
In natural skincare, raw citrus juices and extracts provide citric acid alongside other beneficial compounds like vitamin C and bioflavonoids. However, applying straight lemon juice to skin is not recommended: the concentration is unpredictable, the pH can be too low (around 2.0), and the furanocoumarins in citrus peel can cause photosensitivity reactions.
At the concentrations used in most skincare products (below 5 percent for pH adjustment), citric acid is very safe. At higher AHA concentrations (10 to 20 percent), it can cause tingling and sensitivity. As with all acids, sunscreen use is important when using citric acid as an exfoliant.
Yes, when used at exfoliating concentrations. By dissolving dead cells and promoting turnover, citric acid helps reduce the appearance of dark spots, dullness, and uneven tone. It also has mild antioxidant properties that support skin brightness.
It is not recommended. While lemon juice contains citric acid, it also contains furanocoumarins that can cause severe burns and hyperpigmentation when skin is exposed to sunlight (phytophotodermatitis). Formulated products with controlled citric acid concentrations are safer and more effective.
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