Vitamin C is a water-soluble vitamin which the body cannot produce itself and which must therefore be ingested through food. It is found mainly in citrus fruits and fresh vegetables. Many processes in the human body require vitamin C. For example, vitamin C has an effect on the optimal functioning of the immune system. Vitamin C is used to build up connective tissue (collagen), helps in wound healing and against tuberculosis. The antioxidant properties of vitamin C are particularly appreciated. On the one hand, ascorbic acid protects cosmetic products from spoilage by contact with oxygen (oxidative spoilage). On the other hand, vitamin C reduces oxidative stress on the skin.