Alcohol dehydrogenase provides a line of defense against a common toxin in our environment . But alcohol dehydrogenase also modifies other alcohols , sometimes producing even more dangerous products . Methanol , which is commonly used to " denature " ethanol rendering it undrinkable , is converted to formaldehyde by alcohol dehydrogenase . The formaldehyde then causes severe damage , attacking proteins and embalming them . Small amounts of methanol cause blindness , as the sensitive proteins in the retina are attacked , and larger amounts , perhaps a glassful , lead to widespread damage and death .