When you think of body horror, David Cronenberg likely pops into mind. The director’s earlier horror films cornered the market on gruesome, psychologically twisted transformations and breakdowns of the human body, after all. But body horror existed long before, with Mary Shelley’s Frankenstein an earlier example, and the sub-genre has thrived and evolved long since Cronenberg left horror. Horror is a genre that flourishes on fear of the unknown, and this sub-genre exploits that fear in the worst possible way.

Body horror is a reminder that sometimes death is better, as we watch in disgust while the victims are trapped inside their own bodies as it degenerates and mutates into something unfamiliar and unidentified. On a visceral level, it disturbs because it’s disturbing and gross to look at. On an emotional level, though, body horror instills a deeper level of fear because we tend to fear losing who we are as people. Seth Brundle’s slow mutation into the Brundle-fly monster in The Fly visually repulsed as his teeth fell out and he vomited digestive enzymes to eat, but his story evoked sympathy due to his desperation to cling to whatever humanity he had left. His transformation was consuming him body and soul.

Body horror as we now know it really began to emerge in the 1950s, with The Fly and The Blob. Both standouts of horror for its time, both a showcase of practical effects, and both would eventually get remade decades later. The most prominent entry in body horror in the ‘60s was, surprisingly, Rosemary’s Baby. Roman Polanski’s classic horror film explored the fears of motherhood, and poor Rosemary Woodhouse (Mia Farrow) never truly had autonomy over her own body. Her own husband drugged her and offered her up to Satan, and the resulting pregnancy was controlled at every turn by the surrounding witches. Even when the Antichrist baby in her womb was making her very ill.

1977 propelled body horror forward in a major way with David Lynch’s Eraserhead, William Sachs’ The Incredible Melting Man, and Cronenberg’s Rabid. Cronenberg had already began his exploration of body horror with 1975’s Shivers, but Rabid broadened the scope of the horror as lead Marilyn Chambers’ Rose found herself patient zero for a zombie outbreak thanks to an experimental procedure that was thrust upon her post motorcycle crash. The Incredible Melting Man followed astronaut Steve West (Alex Rebar) slowly melting away upon his return to Earth following serious radiation exposure in space. Narratively, the film is rather dull, but it’s memorable for Rick Baker’s fantastic makeup effects work that makes West’s slow disintegration so gnarly. Lynch gave a surreal twist to body horror with Eraserhead, as Henry Spencer (Jack Nance) learns to care for and cope with a deformed child. It’s strange and dreamlike.

The golden age of practical effects in the ‘80s, meant body horror exploded. 1980 saw another entry in the surreal, with Ken Russell’s Altered States. Starring William Hurt in his debut role, he played Dr. Eddie Jessup, a professor seeking an alternate plane of existence by way of drugs and deprivation chambers. Jessup morphs and transforms with each experiment in the chambers. Two years later brought John Carpenter’s The Thing, a masterclass in paranoia and practical effects, as the Antarctic research team is hunted by a shape-shifting alien that assumes the appearance of its victims. Cronenberg’s Scanners, Videodrome, The Fly, and Dead Ringers firmly established the director as a defining voice in body horror. But there’s also one oft-overlooked voice that played an integral role in ‘80s body horror; H.P. Lovecraft.

Stuart Gordon’s love of Lovecraft delivered gooey, slimy, gory body horror in the form of Re-Animator and From Beyond. Re-Animator, loosely based on short story Herbert West-Reanimator, followed the exploits of Jeffrey Combs’ Herbert West as his reanimating agent leads to serious undead trouble. From Beyond sees Jeffrey Combs once again in the lead as Dr. Crawford Tillinghast, a survivor of Dr. Pretorius’ alternate reality experiments gone wrong. Pretorius’ machine opens the portal to an alternate world that leaves humans in extended close proximity forever morphed. Gordon’s producing partner Brian Yuzna would tackle gooey body horror of his own in 1989’s Society, though the body horror would remain subtle into the surreal final act infamously known as the “shunting.”

Clive Barker merged body horror with hell in 1987’s Hellraiser, as Frank Cotton’s reverse resurrection was the gory stuff of nightmares. Throw in sadomasochism and self-mutilation, and Hellraiser further broadened the scope of body horror. Japan was also experimenting with body horror in the late ‘80s, exploring government tests via animation in Akira and extreme metal meets man body horror in Tetsuo: The Iron Man.

If you thought the ‘90s were a wasteland of body horror, then seek out Braindead (Dead Alive) and Body Melt. The former takes a comical approach to the zombie outbreak and injects it with an insane amount of gore and body horror. The latter sees residents of a small town being used as test subjects for a drug that causes painful death by way of rapid decomposition. Both films take body horror to gag-worthy levels and it’s recommended that you skip out on eating while watching.

It wasn’t until the following decade, though, that body horror would return in a big way. Eli Roth’s Cabin Fever made you afraid of infection with the flesh-eating virus at the center of the film. James Gunn injected humor in body horror with Slither, its alien invasion leading to all forms of grotesque mutations. Then there’s The Human Centipede, a horror film that seeks to offend based on premise alone; a mad scientist seeks to create a human centipede by stitching his kidnapped victims together, rectum to mouth.

A new trend in body horror started to emerge; the coming of age horror story. Teeth, Ginger Snaps, Raw, and Blue My Mind all took the horrors of female puberty and twisted it further with strange body transformations. In Ginger Snaps, the onslaught of puberty was represented with Ginger’s oncoming infection of lycanthropy, while transitioning into womanhood meant transforming into a wholly different beast in Blue My Mind. Teeth and Raw interpreted sexual awakening with monstrous results.

Body horror overlaps and blends well with other sub-genres of horror, and offers more internal depth than just outward body transformations. It may have begun rooted in conscious fears of losing control of our own bodies as the characters on screen lost control of theirs via mutilation, transformation, or decomposition. Now it can reflect our medical fears, unwanted change, technological fears, and even fears of natural growth. This is only a tip of the iceberg, so be afraid. Be very afraid.