Citric acids found in lemons and limes are the fruit acids that work extremely well as cleaning agents. Citric acids basically act as an antioxidant and is most commonly found in lemons and limes even though they are found in other fruits.
Citric acid is actually used in several different things. Some of these uses include flavoring in soda, keeping fats from separating in ice cream, preventing crystallization in caramel, and dissolving rust from steel. It is often used in shampoo to help wash out hair dye and wax from human or pet hair. Citric acid is found in almost all cosmetic creams and gels, but it does not have to be included in the ingredients list since it is considered to be a processing aid instead of an actual ingredient.