What exactly is citric acid? It's an acid compound naturally found in citrus fruits, but it can also be derived from mold-based fermentation (e.g., Penicillium or Aspergillus niger) of sugars.
As noted in ChemIDPlus Lite, an on-line database by the U.S. National Library of Medicine, and PubChem, a database by the National Center for Biotechonology Information (NCBI), here are a few of the names citric acid may go by:
Aciletten; Anhydrous citric acid; Chemfill; Citrate; Citric acid, anhydrous; Citro; Citretten; Hydrocerol A; Kyselina citronova; 2-Hydroxy-1,2,3-propanetricarboxylic acid; 1,2,3-Propanetricarboxylic acid, 2-hydroxy-; 2-Hydroxypropanetricarboxylic acid; 2-Hydroxytricarballylic acid; 3-Carboxy-3-hydroxypentane-1,5-dioic acid; 2-hydroxypropane-1,2,3-tricarboxylic acid
Molecular Formula: C6H8O7
Citric acid is a chelating agent, bactericide, fungicide, anticoagulant, agricultural chemical, therapeutic agent, sequestrant, and hematologic agent.
Because citric acid kills bacteria, mold, and mildew, it's great for general disinfecting and cleaning. It's also effective at removing soap scum, hard water stains, calcium deposits, lime, and rust. In addition, it serves as a preservative in many cleaning solutions. Because lemon juice contains 5 - 8% citric acid (per PubChem), it's often used in green cleaning, such as in this Clean Everything Lemon-Lime Spray.
Citric acid is used in several cleaning products, such as auto cleaning products (e.g., wheel and radiator cleaners), metal cleaners, oven cleaners, dishwasher cleaners, all-purpose cleaners, soap-scum removers, bathroom cleaners, tub & tile cleaners, carpet cleaners, dish soaps, laundry detergents, air fresheners, window cleaners, stain removers, and dishwasher rinse aids.
In addition to its use in cleaning products, citric acid is used in a variety of other industries, such as the personal care, agricultural, food, pharmaceutical, and electroplating industries. In the food industry, it serves as a preservative, flavoring agent, and vegetable rinse. In personal care products, it's used to add an effervescent quality (e.g., bath bombs), to adjust pH, and to serve as an alpha hydroxy acid (e.g., anti-aging creams). You'll find it in shampoos, hair colorants, antibacterial wipes, liquid hand soaps, body gels and washes, conditioners, eye pencils, deodorants, baby wipes, nail enamels, peels, creams, etc. It's also used in some supplements and pharmaceuticals (e.g., vitamin powders, syrups, elixirs). Finally, the agricultural industry uses it as a pesticide to treat crops.
Product Brands Containing Citric Acid
To see if certain products contain citric acid, try searching the U.S. Department of Health and Human Services Household Products Database, the Environmental Working Group's (EWG) Guide to Healthy Cleaning, the Good Guide, or the EWG's Skin Deep Cosmetic Database. Remember, if using the general term "citric acid" doesn't generate a lot of results, try entering one of its synonyms.
Checking out product reviews on About.com is another good source, too.
When citric acid is used in personal care products, food, or drugs it is monitored by the U.S. Food and Drug Administration (FDA). For other uses, such as pesticides and cleaning products, it is monitored by the Environmental Protection Agency (EPA). The last official review of citric acid was done by the EPA in 1992.
Health & Safety
According to the EPA, citric acid is GRAS or "generally recognized as safe." However, citric acid does have some safety and health concerns as noted in the National Institute for Occupational Safety and Health's (NIOSH) International Chemical Safety Card (ICSC) on citric acid.
Breathing in citric acid can cause respiratory symptoms, such as cough, shortness of breath, and a sore throat.
Contact with the eyes can result in redness and pain, and skin contact may cause redness as well. Also, ingesting citric acid can cause abdominal pain and a sore throat. Due to these concerns, NIOSH suggests preventive measures for those working with citric acid, such as protecting the skin and eyes and providing appropriate ventilation.
Citric acid is naturally found in food and water and readily biodegrades in the environment, so no significant negative effects are expected from its use according to the EPA's R.E.D. Fact Sheet on the chemical.