pH value is a measure of the activity of hydrogen ions in a solution and determines whether the solution is acidic or alkaline. The pH of a cosmetic product is very important for proper skin care. The skin’s acidic pH plays a protective role, and products with a low pH can only exert their effect under those conditions - for example, fruit acids, which can have a pH as low as 1.5. The natural pH of the skin is 5.5, which means it is important to use skincare products with a matching pH to maintain this balance.