Citric acid is a weak organic acid that occurs naturally in produce, such as citrus fruits. It is used in food, cosmetics, and cleaning products. Citrus fruits such as lemons and limes have the highest amounts of naturally occurring citric acid. Other fruits and vegetables also contain some natural citric acid, but in lesser amounts. These include oranges, grapefruits, tangerines, pomelos, pineapple, strawberries, tomatoes, broccoli, and carrots. Citric acid is also found in all plants and animals in small traces. However, the citric acid that is added to food and drinks, medications, personal care products, and cleaning products is artificial. This type of citric acid is created from a type of black mold and can cause allergic reactions in some people. It is produced from crude sugars, such as molasses and corn starch, by the mold Aspergillus niger.