Citric acid is the acid that makes lemons sour, and the reason limescale gives up. It dissolves scale, then holds the freed calcium and magnesium so they cannot form new scale. One catch: marble, limestone and travertine are mostly the same mineral as limescale, so acids can etch them too.
Quick facts
- What it is: a weak organic acid, C6H8O7
- Its job in our products: descaler and chelating agent
- Smell: none (PubChem describes it as odorless)
- EPA Safer Choice: green circle
- EWG grade: A (see the EWG page)
- CAS number: 77-92-9
How it clears scale and spots
Citric acid dissolves limescale, which is mostly calcium carbonate. Its three acid groups and one hydroxyl group give it several places to grip a metal ion, which makes it a good chelator. That helps clear cloudy residue and water spots.
In our dishwasher tabs and powder the wash is alkaline, so citric acid is neutralized to citrate, which mainly holds hard-water minerals in solution (see sodium citrate).
Made by mold, not squeezed from lemons
More than 90 percent of world production is fermented, mainly by the mold Aspergillus niger fed on sugar sources such as glucose syrup or beet molasses. The mold is filtered out and the acid is purified and crystallized, so we describe it as fermentation-derived. Our sodium gluconate starts from sugar too.
Is citric acid bad for you?
For food, the FDA lists citric acid as generally recognized as safe (GRAS) under 21 CFR 184.1033. That is a food-use status, and our products are not food. For cleaning products, the detergent industry's HERA risk assessment estimated household exposure at several orders of magnitude below the no-effect level in rat studies, and small next to what we eat, and found no safety concerns for consumers. Its main hazard is irritation, mostly of the eyes.
Citric acid has a green circle from EPA and an A from EWG, for the ingredient rather than our finished products (how we vet ingredients). HERA also found it readily biodegradable, rapidly broken down in sewage treatment and rivers, with low acute toxicity to fish, water fleas and algae.
Handling and safety
Concentrated citric acid causes serious eye irritation, but in use it is diluted and rinsed away. Never mix cleaning products, especially an acid with chlorine bleach: the two react and release chlorine gas. Acids can etch natural stone, so check the label before using our sprays on it. If any gets in eyes, rinse cautiously with water for several minutes. If any is swallowed, call Poison Control at 1-800-222-1222. Store tablets, powders and refills in their pouch, up high or in a latched cabinet, out of reach of children and pets.
Where you'll find it
- Sprays and refills: All-Purpose Cleaner refills and spray kits (Fragrance-Free and Lemongrass), Bathroom Cleaner refills and spray kit (Lavender), Glass & Mirror Cleaner Refills
- Dish: EWG Verified Dishwasher Tabs, EWG Verified Dishwasher Powder
- Kits and bundles: Home Kitchen Kit, Dish Starter Kit, Ultimate Home Bulk Bundle, Expert Home Cleaner Kit, Complete Surface Cleaner Starter Kit, Refill Cleaning Bundle
All are fragrance-free except the Lemongrass, Lavender and Glass & Mirror sprays, which are scented with essential oils, and the last three kits listed, which include those sprays. Each product page has the full ingredient list.
Sources
- America's Poison Centers. (n.d.). Poison Help. https://poisoncenters.org/
- Citric acid, 21 C.F.R. § 184.1033. https://www.law.cornell.edu/cfr/text/21/184.1033
- Environmental Working Group. (n.d.). EWG's Guide to Healthy Cleaning: Citric acid. https://www.ewg.org/cleaners/substances/1281-CITRICACID/
- HERA Project. (2005). Citric acid and salts (CAS 77-92-9, 5949-29-1, 6132-04-3) (Edition 1.0). Human and Environmental Risk Assessment on Ingredients of Household Cleaning Products. https://www.heraproject.com/substance/citric-acid/
- Latif, A., Hassan, N., Ali, H., Niazi, M. B. K., Jahan, Z., Ghuman, I. L., Hassan, F., & Saqib, A. (2025). An overview of key industrial product citric acid production by Aspergillus niger and its application. Journal of Industrial Microbiology & Biotechnology, 52, Article kuaf007. https://doi.org/10.1093/jimb/kuaf007
- National Center for Biotechnology Information. (n.d.). PubChem compound summary: Citric acid. https://pubchem.ncbi.nlm.nih.gov/compound/Citric-acid
- National Center for Biotechnology Information. (n.d.). PubChem compound summary: Sodium hypochlorite. https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-hypochlorite
- Natural Stone Institute. (n.d.). Learn about cleaning products for natural stone. https://www.naturalstoneinstitute.org/consumers/care/
- U.S. Environmental Protection Agency. (n.d.). Safer Choice: Safer Chemical Ingredients List. https://www.epa.gov/saferchoice/safer-ingredients
