Hyaluronic acid is present naturally in almost all tissues of the human body as one of the most hydrophilic molecules, which is rightly called "natural moisturizer". 

Hyaluronic acid gives the skin and joints the cooling hydration they need. It is a carbohydrate (mucopolysaccharide) that is found naturally in all cells of the human body, with its highest concentration in synovial fluid and connective tissue.