Formalin is an aqueous solution with formaldehyde, a colourless, water-soluble gas. Usually formalin contains methanol as a stabilising agent. The solution is often used as a disinfecting agent. A 85-year-old woman was admitted to the emergency department with altered levels of consciousness after she accidentally drank formaldehyde cleaning detergent. She was treated with intravenous folinic acid in order to increase the elimination rate of formic acid. However, she rapidly developed signs of shock with multi-organ failure requiring symptomatic treatment, including intubation, supportive vasopressor treatment and renal replacement therapy, and recovered with time and intensive treatment. The literature suggests that intoxication with formalin is fatal. We present a case of an elderly lady surviving a severe illness caused by a moderate formalin intoxication. © 2017, Netherlands Society of Intensive Care. All rights reserved.