Patrons watching the new horror flick Raw at the Toronto International Film Festival couldn’t stomach the scenes of blood, guts, and gore, resulting in some fainting and reports of people getting sick.

While this spin on the classic zombie narrative (less undead, same amount of people eating) is not the first movie to make people sick, it’s a reminder of the power phobias have over the body. The Diagnostic and Statistical Manual of Mental Disorders groups blood phobia within the gnarlier group of blood-injection-injury phobia; an estimated three to four percent of the American population suffers from this. When they see blood and guts, their blood and heart pressure increase.

A still from the movie “Raw.”
Girl, don't eat that.

A sudden drop in heart and blood pressure causes fainting, nausea, and dizziness. This doesn’t happen to other phobics, whether it be flying or black cats. According to John Sanford of Stanford Medical School, this is due to a vasovagal response. That’s when the vagus nerve, a part of the parasympathetic nervous system, overacts and enacts an “involuntary ‘rest and digest’ function.” One’s heart rate lowers, the secretion of gastric juices accelerates, and the chances of getting a one-way ticket to vomit town increases.

There’s not a consensus, but researchers think that this reaction may be a “fight-or-flight” response. Fainting — or nearly fainting — is another form of fleeing; your body is saying okay buddy, it’s time to play dead.

Repeated exposure to blood, as well as consuming caffeine and sugar, is known to help keep people from becoming lightheaded. So if you’re thinking of seeing Raw, consider gearing up with some other gory movies beforehand and getting that extra large Big Gulp so you don’t lurch.

Photos via Petit Film/Rouge International/Frakas Productons, Petit Film/Rouge International/Frakas Productions