Citric Acid is derived from citrus and used primarily to adjust the pH of products to prevent them from being too alkaline or acid-alkali balance. It is also a mild preservative and sequestering agent. In high quantities it acts typically as an exfoliatory AHA.
Although Citric Acid is often used to lower the pH of personal care products, it can be very irritating for some people, much more so than other Alpha Hydroxy Acids. Lactic Acid is another of the Alpha Hydroxy Acids that can be used in stead due to its more gentle nature on the skin.
It is used in shampoos, conditioners, shower gels and in bath bombs, mixed with sodium bicarbonate makes the water fizz