What Is Potassium Hydroxide?

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Potassium hydroxide, also known as potassium hydrate and caustic potash, is a strong alkaline chemical available in pellets and flakes. With the chemical formula KOH, potassium hydroxide is one of the compounds people call lye. Potassium hydroxide is included in cleaning products, and has uses in industry and in medical diagnostics. It also has a role as an alternative health product.

Diagnostic Use

Some dermatologists use potassium hydroxide to diagnose fungal infections in skin, hair and nails. For skin infections, laboratory personnel mount a skin scraping and apply potassium hydroxide to dissolve the epidermal cells and expose the fungal structure, explains an article in the "Indian Journal of Dermatology, Venereology and Leprology." The authors note that potassium hydroxide is more reliable than lab cultures for identifying the presence of fungi that cause skin disease.

pH Value

Potassium hydroxide has very high alkalinity as measured on the pH scale. This scale goes from 0 to 14 and defines the acidity or alkalinity of a substance, with 7 being neutral, and alkaline being higher than 7. Pure distilled water has a pH of 7. Potassium hydroxide has a pH of 12 to 14. Compare this to ammonia at 10 to 11, and borax at 9.


Some people believe that alkaline water is best for health. Advocates claim that drinking alkaline water is beneficial for health because disease and aging result from excess acid accumulation in the body. Alkaline water supposedly neutralizes this acidity. Commercial liquid products are available with highly diluted potassium hydroxide that change regular drinking water into strong alkaline water, similar to the pH level created with a water ionizer. You add drops of the solution as directed to drinking water. The theory behind drinking alkaline water for health is pseudoscience, according to chemist Stephen Lower, retired faculty member of Simon Fraser University.


Potassium hydroxide pellets and flakes are considered poisonous, and combining the chemical compound with water or other moisture turns it into a caustic substance. Swallowing potassium hydroxide can have severe and even life-threatening effects, as noted by MedlinePlus. It may result in burns to the mouth, throat, esophagus and stomach; severe mouth, throat and abdominal pain; diarrhea; throat swelling shut; and a swift drop in blood pressure, which is a symptom of a shock reaction.

Poisoning Treatment

MedlinePlus notes that immediate medical attention is needed if you or anyone you know has swallowed potassium hydroxide. Recovery depends on how quickly treatment is received. Flush away any of the chemical compound from the skin with lots of water. Do not make the affected person vomit unless medical personnel tells you to do so. Medical treatment may include breathing support, a breathing tube, intravenous fluids and pain-relieving medication.