Vitamin C (THDA)

Vitamin C (THDA) is an oil-soluble form of vitamin C that overcomes two main weaknesses of pure ascorbic acid – its instability and poor penetration into the skin. The ascorbic acid molecule is protected by fatty acid residues, so the ingredient passes through the skin barrier more effectively and remains stable in a formulation for longer without oxidation. In the skin, THDA is gradually converted to active vitamin C by skin enzymes. According to a study cited by the manufacturer, this conversion reached approximately 84 % in a reconstructed skin model. The ingredient therefore acts as a reservoir form of vitamin C that is activated directly where it needs to work. Key benefits Antioxidant protection – once converted to vitamin C, it helps neutralise free radicals generated in the skin by UV radiation and environmental factors. Even skin tone – according to the manufacturer's studies, its antioxidant action helps prevent UV-induced pigmentation. It is therefore suitable for brightening products and products targeting uneven skin tone. Formulation stability – compared to pure ascorbic acid, it oxidises significantly more slowly, so the product does not brown quickly and retains its efficacy. Skin compatibility – it does not have the acidic character of pure vitamin C, so the formulation does not need to be strongly acidic. Use in formulation The ingredient is oil-soluble – it is added to the oil phase or directly to an anhydrous base. Processing temperature is critical: below 40 °C is recommended. In emulsions, therefore, add the ingredient during the cool-down phase, not t