Horror movies are as much a mainstay of Halloween as trick or treat − but why are they so bloody?

Horror movies are plentiful in 2024, and plenty bloody. The year has seen the release of films awash in blood, such as “Immaculate,” “The First Omen” and “The Strangers.” With Halloween on the way, bloody offerings are streaming, in theaters and running in marathons on cable.

Watch them, and you’ll likely notice that as the decades pass, the directors, writers and studio executives of these films seem to produce more and more on-screen blood, violence and gore. But why?

As a professor of horror studies, I explore the depths of the genre with my students – and for us to understand the evolution of blood in horror cinema, we first consider how films reflect their times.

Alfred Hitchcock and Michael Powell created proto-slashers with “Psycho” and “Peeping Tom,” respectively. Both films were released in 1960 about four months apart, both feature serial killers, and both operate on a “tell, don’t show” visual aesthetic. Rather than show the blood to the audience, the films provide narrative cues to only suggest the blood.

Guts, gore and so much more

In “Psycho,” Marion Crane, played by Janet Leigh, is stabbed to death in the famous shower scene. But the quick-cut editing gives only the illusion of her nude body being slashed as a small amount of blood washes down the drain in black-and-white tones. By not shooting “Psycho” in color, and avoiding the image of bright red blood in the bathtub – Hitchcock’s choice – the film doesn’t seem as violent.

By the late 1960s, the restrictive Hays Code, which prohibited overt on-screen violence and the use of fake blood, was replaced by the less stringent Motion Picture Association of America film ratings system. Filmmakers could latch onto new freedoms to express fear, anxiety and dread in more visceral depictions. One way to do that – more blood.

In “Night of the Living Dead,” George A. Romero’s 1968 seminal zombie flick, the walking dead consume the flesh of the living. Even though the movie is in black and white, the monochromatic presentation does not dull the display of the undead gobbling guts and licking up blood.

The film’s release came six months after the assassination of Martin Luther King Jr., and a clear connection between Romero’s film and the Civil Rights Movement then taking place is apparent. The movie’s heightened gore correlates to the movement’s all-too-bloody violent struggle, as Ben, played by Duane Jones, the sole person of color among the living, hides from the ghouls in an abandoned farmhouse with a group of six white people.

Ben works to keep the group safe but faces ongoing pushback from the white male characters. At the end of the film, a group of vigilantes, believing Ben is a zombie, guns him down before tossing his body into a fire.

The symbolism as a reflection of the times is hard to miss. Romero and John Russo, who co-wrote the screenplay, didn’t initially intend to make a statement on civil rights; but later, during postproduction, Romero realized the assassination of King turned his movie into a “Black film.”

Bloody metaphors

Then came the 1970s, when blood was sprayed all over the screen. But Tobe Hooper’s “The Texas Chain Saw Massacre” (1974), William Friedkin’s “The Exorcist” (1974) and Ridley Scott’s “Alien” (1979) have something else in common: They feature women protagonists who survive the unthinkable.

Once again, blood is a common denominator. Sally’s body is covered in it after escaping Leatherface; Regan’s body, along with the blood, spews green vomit; and Ripley sees an alien burst out of a crew member’s chest. But the films weren’t just gory – they were metaphors for the uphill battle for women’s rights in the 1970s.

The original “Halloween” (1978) also fits here, but with a twist. The character of Laurie Strode, perhaps an early prototype of women protagonists in horror films, connects back to a “tell, don’t show” sensibility while simultaneously embracing changing times. While the first kill shows Michael Myers stabbing his older sister, the audience views the death from the partially veiled perspective of Myers behind his Halloween mask. You see little until her body hits the floor to reveal the blood.

Nightmares and reality

In the 1980s, the slasher subgenre dominated horror – and the bloodier, the better: These movies focus on the number of kills and the creative ways the victims are dispatched.

Each sequel in these horror franchises needed to up the kills, if for no other reason than to outdo its predecessors and competitors. Audiences began rooting for villains like Myers, Jason Voorhees and Freddy Krueger, all of whom had their own theme music, and in Freddy’s case, trademark one-liners. Many of the villains had more character development than their victims, who seemed interchangeable and little more than fodder for the slasher machine.

The 1990s had bigger-budgeted, more innovative films, such as Wes Craven’s “New Nightmare” (1994) and “Scream” (1996). Here the attacks are more personal; the stabbings are close-up. CGI, or computer-generated imagery, used in abundance in the “Nightmare” series, allowed for more creative and bloody kills.

Scarier times mean bloodier movies

Since 9/11, horror films have existed in a place where there’s no apparent motive other than violence and bloodshed. In “The Strangers” (2008), the villains tie up, torment and savagely maim their victims. In the 2009 remake of “The Last House on the Left,” it’s the villains who meet a bloody end. Contemporary horror understands how senseless killings on screen are effective, because the removal of emotion from the violence parallels real-world incidents.

By the late 2010s, horror films link to the #MeToo and Time’s Up movements, most notably in the “Halloween” reboot trilogy, as Laurie Strode once again confronts Michael Myers and the trauma he inflicted 40 years prior.

The kills in the new “Halloween” trilogy are extremely bloody and violent. They also mirror the sexual and societal exploitation of women and their bodies. Ultimately, the series allows the protagonist, and the traumatized town of Haddonfield, to acknowledge the evil, confront it and try to finally put an end to it, once and for all.

The evolution in the horror genre’s presentation of blood and gore doesn’t necessarily make for scarier movies, but they often point to the scarier times in which we live. Earlier horror films, comparatively tamer and with less blood, were often box-office successes. But today’s audiences probably appreciate them more for their artistic merits than the fear they induce.

The preferences of horror audiences change over time, much like the ebb and flow of the blood depicted in these movies. The original “Halloween” has hardly a drop; the recent reboots are over the top – but still nowhere close to the mayhem depicted in the just-released “Terrifier 3.”

What the future holds is anyone’s guess. But check out the world around you, and you’ll certainly get a bloody good hint of what’s to come.

James Francis, Jr. does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.