This is correct it irritates the lining of the stomach. I don't know how folk who drink blood manage not to barf but I've read from a few sources that long term blood drinking can lead to hemochromatosis. Which can really mess up and destroy the liver. Heres one source about the dangers of blood drinking: So I'd assume some people manage to drink blood somehow but I am unsure how. Maybe they just don't drink large amounts at one time and over time it causes that damage. Idk.As far as I know, and someone correct me if I'm wrong, blood acts as an emetic agent on humans, meaning that you'd barf everything up if you drink more than a certain amount of the red stuff. Or does that guy claim that he's able to alter his metabolism?