Being sick is a real energy drainer. Anything from the smallest sniffle to the harshest flu will suck the mojo right out of you, and you won't feel like doing anything; including brushing your hair.
That's where this trope comes into play. Bedhead-itis refers to when a character in media has messy hair when they are sick, as a visual indicator of how messy they feel on the inside.
Subtrope of Messy Hair. Compare Expressive Hair (where hair changes based on general emotions), Bad Hair Day (where this trope is not connected to illness), Illness Blanket (where a blanket is used as a visual indicator of illness), and Sickness Equals Redness (where a red nose/cheeks indicate illness). No relation to Alt Itis or Something Itis.
- Toyed with in the Noonbory and the Super 7 episode "Tooba-Achooba!"; when the Super Sensors come down with the Tooba-Achoobas, Jetybory, who has Ears as Hair, gets her ears literally bent out of shape, and Totobory, who has Prehensile Leaves in place of hair, has his leaves flop down and become unusable.
- A variant in Leafie, a Hen into the Wild; Leafie's feathers grow messier as the unsuitable environment takes its toll on her body.
- Bad Kitty: Downplayed and later subverted in "Bad Kitty Goes to the Vet". Kitty is thought to be sick because she's refusing to eat, but her fur is just a little mangled. Turns out, she's not actually sick; she has a toothache.
- Felicity Floo Visits the Zoo: The titular Felicity goes to the zoo while she has a cold and her hair is quite unkempt.
- In the Sesame Street book "Nobody Cares About Me!", Ernie's hair is even more unkempt than usual when he's in bed with a cold.
- In the Central Park episode "Garbage Ballet", Paige's hair becomes messy when her illness starts making her think there's a rat infestation.
- Dan Vs.: In "The Common Cold", Dan has a cold and his hair gets even messier than it usually is.
- In the Dexter's Laboratory episode "Germ Warfare", Dee Dee's illness makes her hair go wild.
- In the Frozen (2013) short Frozen Fever, Elsa's braid becomes ratty when her cold begins to make her loopy.
- In the Grossology episode "Yack Attack", Abby's bangs become slightly ratty after the contaminated water makes her sick.
- Kim Possible: In "Sick Day", almost everyone who catches a cold (Kim, Shego, and Ron) ends up with frazzled hair.
- In The Loud House, some of the Loud siblings get ratty hair as a result of their illness in "One Flu Over the Loud House".
- In one segment of the "Sneezes and Hiccups" episode of The Mr. Men Show, what little hair Mr. Stubborn has is messy when he has a cold.
- Invoked in the My Gym Partner's a Monkey episode "Sick Day", where Adam purposely messes up his hair while Playing Sick.
- My Little Pony: Friendship Is Magic:
- Two examples courtesy of Pinkie Pie:
- In the episode "Applebuck Season", her mane becomes frazzled while she is suffering from food poisoning thanks to Applejack messing up the recipe.
- Downplayed in "28 Pranks Later". She appears to be ill as a supposed first stage for the Zombie Apocalypse after she's eaten some cookies that Rainbow has used for a prank, but her mane's only a little messy. Subverted, however, as Pinkie is actually faking it so that everyone can prank Rainbow Dash right back.
- In "The Saddle Row Review", Coco Pommel has a cold and her mane is quite unkempt.
- Two examples courtesy of Pinkie Pie:
- In "Eclipse Lake", an episode of The Owl House, Luz has mess(ier) hair than usual when she has the common mold.
- The Ren & Stimpy Show: In "Nurse Stimpy", Ren has an unspecified illness and the hairs on top of his head are somewhat scraggly. At the end of the episode, Stimpy is ill as well, and the hairs on his head are messy, too.
- Total DramaRama: In "Germ Factory", the kids deliberately get sick so they won't have to go to school, and Courtney and Bridgette end up with mangled hair.
- In Yin Yang Yo!, Yin's fur is messy when she has the Woo Foo Flu.