Some brands of rubbing alcohol feature up 99 percent alcohol concentration. Nonetheless, this isn’t the same kind of alcohol you are meant to drink, and it certainly has nothing to do with proof. Per UpToDate, 250 mL of isopropyl rubbing alcohol can be lethal when consumed. The chemical can seriously harm the esophagus and lungs, in addition to inflicting side effects similar to narcotics with its fumes alone.