Skin contact with the solid hydroxides or concentrated solutions can cause rapid tissue destruction and severe burns.
Potassium hydroxide is somewhat more corrosive than sodium hydroxide.
Contact with even dilute solutions will also cause skin irritation and injury, the severity of which will depend on the duration of contact. Eye exposure to concentrated sodium hydroxide or potassium hydroxide solutions can cause severe eye damage and possibly blindness. Ingestion of concentrated solutions of sodium hydroxide or potassium hydroxide can cause severe abdominal pain, as well as serious damage to the mouth, throat, esophagus, and digestive tract. Exposure to high concentrations may result in delayed pulmonary edema. Repeated or prolonged contact may cause dermatitis.