Formaldehyde is a highly reactive chemical used as a preservative and also in many industrial processes. In our cells, this aldehyde is generated as a by-product of several essential biochemical pathways. This ‘endogenous’ formaldehyde is very reactive and can damage proteins and DNA resulting in lethal toxicity. Therefore, cells harbour two protective barriers: the formaldehyde-detoxifying enzyme alcohol dehydrogenase 5 (Adh5) and the Fanconi Anemia DNA repair pathway. The simultaneous inactivation of these two systems leads to haematopoietic stem cell attrition, kidney and liver dysfunction, and development of cancer in mice. My work aims to understand the molecular mechanisms that counteract unwanted consequences of essential metabolism.