Sometimes, the consumption of local made alcoholic beverages may cause blindness or even death. This may be because of contamination of the beverages with :

Ethanol (ethyl alcohol) is the alcohol intended for consumption in alcoholic beverages. Methanol (methyl alcohol) is a highly toxic substance that can be produced as a byproduct during improper fermentation or distillation, or sometimes illegally added to beverages. When ingested, methanol is metabolized by the body into formaldehyde and formic acid, which are potent toxins that damage the optic nerve (leading to blindness) and other organs, often resulting in death.