How do you instantly show that a character is suffering from illness of the potentially deadly kind? Make them bald. The reason this visual shorthand works is because the image of the cancer patient who has lost hair to chemotherapy is very well-known. The disease in question usually is cancer, but other illnesses or ailments count too.
Because Women Are Delicate (and are expected to have hair) and Children Are Innocent, the Delicate and Sickly or Littlest Cancer Patient dressed in hospital clothes and hooked up to machines will very often also be bald to hammer in that their illness isn't likely to go away soon. It can also be used as for an Expository Hairstyle Change or a Secretly Dying reveal: where a character introduced with a full head of hair reveals their hair to be a wig or is suddenly seen bald and in a hospital, viewers instantly understand they're being treated for cancer or something just as bad. Conversely, Hair Today, Gone Tomorrow may be used for presently bald patients who have hair in a flashback.
Variations include the sick person wanting to get ahead of their hair loss by shaving their hair off themselves and someone shaving their head in solidarity with a loved one who is suffering from cancer. This can also be exploited by those willing to take advantage of the assumptions people have about sickly-looking bald people. A very common (and seldom lampshaded) phenomenon is for characters with cancer to be bald only on their scalp, although chemotherapy treatment causes all of the patient's body hair to fall out (in fact, it's the [radioactive] chemo treatment that actually causes the hair loss, not the cancer itself), including the eyebrows, which these characters are often shown to still possess.
Compare Ominous Hair Loss, where hair loss means something is wrong (this trope could be seen as the follow-up to that), Prematurely Bald, for when a character (usually male) starts losing hair early, Baldness Angst, for when a character mopes about being bald for whatever reason (sickness included), and Disease Bleach, when stress/illness manifests in a hair color change rather than hair loss. Contrast Bald Head of Toughness and Bald Mystic, for when a bald head indicates a tough or mystical character rather than one that is frail due to illness. See also The Topic of Cancer, which treats cancer as one of the worst and most terrifying diseases; the unnaturalness of hair loss may contribute to that fear.
Not to be confused with the dermal disorder alopecia (an autoimmune disorder that causes spontaneous hair loss), which can be resolved and is not life-threatening by itself (though it is a potential side effect of chemotherapy).
- The Brazilian cancer charity GRAACC created the ad campaign Bald Cartoons, showing bald versions of cartoon characters to help children suffering from cancer cope with their hair loss.
- One of those "Pass It On" public-service ads shows a trio of young men escorting a sick teenage girl to the senior prom, and one of them —apparently her date— has shaved his head clean in solidarity with her. Despite the girl presumably being bald from chemo treatment, she clearly has a shaved head and full set of eyebrows, just like he does.
- In Ojamajo Doremi Na-i-sho a young girl named Nozomi Waku longs to become a witch but suffers from cancer and wears a shamrock green bandanna with teal print over her head due to losing her hair to chemotherapy. Sadly, she doesn't make it, passing away after becoming an Apprentice Witch for one evening.
- Anderson: Psi-Division: Cas is bald after she goes into a virus-induced coma, though she regrows her hair after she's woken up again and returns to duty.
- The Hills Have Eyes: The Beginning: Karen is shown bald shortly before her death, due to the effects of radiation poisoning.
- Killing and Dying: It becomes apparent that Jesse's mother is ill when she shows up to the recital with a cloth cap over her bald head. It immediately recontextualizes her support of Jesse. By the next part of the story, she's dead.
- In the film Pacific Rim, we learn that Stacker's partner blacked out from radiation poisoning during the battle with Onibaba and later died of cancer. The tie-in comics expand on this, first introducing said partner Tamsin with shockingly red hair. When Mako visits her in the hospital later, however, she's very thin and bald save for a few strands of hair.
- Superman & Batman: Generations has an elderly Lois Lane losing her hair to chemo treatments due to her suffering from cancer.
- In The Strange Revenge of Lena Luthor, Supergirl's friend Lena loses her hair after undergoing brain surgery.
- Thor (2014): Mjolnir's mysterious new wielder is a buff, masked woman with flowing blonde hair. Her identity is later revealed to be Jane Foster, who's dying of cancer — and to emphasize this, Jane is much gaunter and completely bald when she detransforms.
- In Zits, Jeremy and Hector assume this has happened to the mother of their friend and bandmate Tim, who reveals that she's been receiving chemotherapy treatment for breast cancer. In response, Jeremy and Hector decide to shave their heads in solidarity. However, it's ultimately subverted, as it turns out Tim's mom didn't lose her hair after all. Regardless, she is genuinely touched by Jeremy and Hector's gesture and gets a good laugh out of it.
- Lampshaded in Bucky Barnes Gets His Groove Back & Other International Incidents. When Natasha gets a buzzcut, Fury compares her to a fifteen-year-old cancer patient.
- Arrival: The protagonist's teenage daughter is briefly shown with a bald head as she dies of cancer.
- Babyteeth: Protagonist Meredith is dying of cancer and has the bald head to prove it.
- In The Best Man Holiday, Mia looks very good for a terminal cancer patient until she takes off her wig to reveal that she's bald.
- Blue Bayou: It was previously hinted that Parker was ill because Antonio meets her at a hospital, but it becomes starkly clear after she takes off her wig to reveal patchy baldness. She is later confirmed to be dying of cancer.
- Florence Foster Jenkins: Florence wears a wig, false eyelashes, and cosmetics to hide that she's lost her hair to syphilis and to her mercury- and arsenic-based medications. By the end of the film, she's on her deathbed.
- Guardians of the Galaxy (2014): Quill's mother is introduced (and promptly killed off) on her deathbed. She's bald-headed and lacks eyebrows, and the sequel outright confirms she was dying of a tumor that Ego the Living Planet planted in her head to kill her.
- Mad Max: Fury Road: Immortan Joe's War Boys all have shaved heads and most, if not all, of them are terminally ill due to radiation exposure, malnutrition and birth defects from living in a post-apocalyptic wasteland.
- My Sister's Keeper: Chronically ill leukemia patient Kate is most often in a hospital gown and a cap to hide her baldness. Later in the film, her mother Sara shaves her head in solidarity.
- Repo! The Genetic Opera: Early on we see Shilo is completely bald, showing her as suffering from a mysterious blood disease that killed her mother; she spends most of the movie wearing a long wig. Subverted when her mother is revealed to have been murdered and her father has been faking her illness to protect her from the Crapsack World outside.
- Elantris: One of the first signs of turning into an Elantrian is the loss of all the victim's hair. Elantrians are all damned to slowly decay and fall into madness due to their immortality and inability to heal.
- Magic Shop: In The Skull of Truth, Gilbert Dawkins returns from being in the hospital, and is completely bald as a result of his treatment. He later confesses to Charlie that he had cancer, and the treatment to make sure it won't come back made all his hair fall out. At the end of the book, one of the signs that he's recovering and has a hopeful future is that his hair is growing back.
- The Midnight Gang: Sally is struck with a serious illness that's implied to be cancer and it's unclear whether she'll live. She's bald, which is said to be from the treatment.
- The Act: Just like in Real Life (see below), Dee Dee Blanchard tries to invoke this by shaving Gypsy Rose's head. This is just one of the things she does (like making Gypsy use a wheelchair in public and force her to submit to medical procedures she does not need) to keep up the pretense that Gypsy has multiple disabilities.
- Battlestar Galactica (2003): Laura Roslin eventually loses her hair due to cancer treatments. She usually wears a wig while in public and a scarf while in private or while exercising.
- The Boys (2019): A mental/psychological version happens with Ashley in season 3, who starts suffering from trichotillomania due to the stress of dealing with Homelander, the show's resident Corrupted Character Copy of Superman. By the season finale, she's wearing a wig to cover up the fact that she's nearly bald from literally tearing her hair out.
- Breaking Bad: Invoked and zig-zagged with Bald Head of Toughness. When Walt begins losing his hair from chemotherapy, he shaves his head and invokes the typical image of a bald cancer patient. However, in the criminal circles he enters, his baldness comes off as more intimidating and his shaving his head coincides with him Taking A Level In Badass by adopting the drug kingpin persona, Heisenberg. Even once he goes into remission, he keeps his head shaved more out of habit and as a sign his Heisenberg persona is becoming his main personality. Ironically, after his remission ends later in the show, he has fully regrown his hair and keeps it that way until he finally dies (and not from the cancer).
- Desperate Housewives: Exploited when people assume one of Lynette's sons has cancer after her twins put bubblegum in his hair, forcing her to shave it all off. Lynette uses her son to play on their sympathies.
- Grimm: Marie's bald head marks her as someone dying of cancer.
- The gang on It's Always Sunny in Philadelphia tries to pass off Mac as a cancer patient by slapping a fake bald cap on his head. In a major win for realism, the person they were hoping to fool rightly points out that chemotherapy would leave Mac without any body hair at all, and he still clearly has eyebrows and a beard.
- In a later episode, Charlie's mom gets cancer and, to raise money for her treatment from a strange medicine man, the gang makes her put on a bald cap and read out an over-the-top sob story so she can get more donations. The sheer level of exaggeration she has to put up with makes her confess to faking her cancer.
- Orange Is the New Black: Rosa's baldness stands out in a cast primarily comprised of female inmates and marks her as the one who has ovarian cancer.
- Infinity Jackson, a teenage girl with cancer from The Politician is bald. It turns out that she has Münchausen's by Proxy — years after this comes to light and she is freed from her oppressive guardian, she has a normal haircut.
- Invoked by Sasha Velour, who won RuPaul's Drag Race season 10, and has said that the reason she does drag bald is to honor her late mother, who lost her hair to and eventually died of cancer.
- Scandal: Supreme Court Judge Verna Thorton is revealed to be suffering from cancer when Olivia walks into her hospital room and she is lying in bed, hooked up to an IV, and bald, having removed her wig. This is an issue as she was aware of her bad prognosis when she was nominated and intentionally hid that from the President and the Senate.
- The Umbrella Academy (2019): Sissy has distinctive blonde curls, so when we see her in 1989 at a hospital with a bald head, it's easy to guess that she isn't long for this world.
- The main character of In Between is a terminal cancer patient, and states that he has gone through chemotherapy, which has led to the loss of his hair.
- Marry My Husband has Jinwon dying of cancer in the first timeline and she was wearing a small cap to cover her bald head.
- Hamster's Paradise: The Severe Infectious Harmster Transmissible Tumor (SIHTT) is a form of contagious cancer that afflicts the Harmsters. One of it's symptoms is that it causes the victim to lose all their fur. This combined with the rot inducing bacteria now inhabiting their bodies, this makes them resemble walking corpses.
- Arthur: In "The Great MacGrady", Mrs. MacGrady loses her hair because of the chemotherapy she's been receiving (though she still has her brown "fur"), so she wears a pink bandanna with white spots to cover it up. Her hair grows back in later episodes.
- BoJack Horseman: Herb Kazazz is a bald man with cancer. Flashbacks reveal him to have had a full beard and a full head of hair.
- Doc McStuffins: Audrey (who is heavily implied to have cancer) is said to be going through chemotherapy, and at one point, she takes her hat off to reveal that she's bald.
- Family Guy:
- Jess from "Married With Cancer" lost her hair to chemotherapy, but after her cancer went into remission, it slowly began to grow back. As Brian is creeped out by her appearance, describing her as looking like a baby doll found in hurricane rubble, Jess takes it as meaning he's calling her his "baby doll".
- In "Road to the North Pole", Brian goes to the mall with Stewie and sees Quagmire with what looks like his nephew. Then Brian talks to them and finds out that it's his niece, and she's bald because of chemotherapy. This causes her to cry, which angers Quagmire.
- Gravity Falls: A variant happens in "Society of the Blind Eye". Old Man McGucket discovers he was once a brilliant scientist who began frequently using a Memory Gun on himself to erase disturbing memories. The side effects of the gun, along with taking his sanity, caused him to go bald. It's difficult to say, however, whether this was because of the gun or because he pulled his hair out and forgot.
- South Park:
- Parodied in "Bloody Mary" where Randy shaves his head after being told that his alcoholism is a disease. It grows back after he's sprayed with the blood erupting from the statue of the Virgin Mary which supposedly gives him the ability to give up drinking.
- Nelson Brown from "Stanley's Cup" has Charlie Brown Baldness as a sign of his cancer.
- Why, Charlie Brown, Why?: Janice Emmons, the Littlest Cancer Patient, ends up going bald due to chemotherapy and a boy laughs at her for her hair loss until Linus sets him straight. At the end of the special, her hair grows back after her leukemia is in remission.
- Dee Dee Blanchard who, among other things, shaved her daughter Gypsy Rose's hair to maintain an appearance of illness in a well-documented case of Münchausen's by Proxy.
- Almost every woman who goes bald, whether by choice or due to a condition like Alopecia that causes hair loss, has to deal with awkward conversations and assumptions of illness when they are really perfectly healthy, often enough that many get annoyed when they are asked about it.