Afflictions and illnesses

Fluttershy with fake pony pox

The following are various afflictions and illnesses featured in My Little Pony Friendship is Magic and accompanying merchandise.

Depiction in the series

Acting like a dog

Screwy acting like a dog.

In The Return of Harmony Part 2, Discord's magic makes Big McIntosh act like a dog. In Read It and Weep, Screwy barks like a hound dog while chasing Rainbow Dash from the hospital.

Airsickness

Shining Armor airsick.

In Once Upon a Zeppelin, Shining Armor gets airsick while on board Iron Will's zeppelin. His face turns green, and he experiences severe nausea and disorientation.

Allergies

Daring Do falsely claiming to be allergic to spiders.

During the episode Bridle Gossip, one of the possible causes Twilight Sparkle considers to explain what turns out to be the effect of poison joke is an allergic reaction.

In Princess Spike, Spike has an allergic reaction to dragon sneeze trees, causing him to have red, puffy eyes and sneeze uncontrollably. In On Your Marks, Apple Bloom states she is allergic to bees. In Triple Threat, Ember is supposedly "allergic to feelings", sneezing in reaction to Thorax sharing his feelings with her.

In My Little Pony Equestria Girls: Friendship Games, Dean Cadance states that Principal Cinch is highly allergic to dogs.

In My Little Pony: Friends Forever Issue #19 Ginger Gold's allergy to strawberries causes her to break out in hives after tasting Rarity's wedding cake. In My Little Pony: Friends Forever Issue #32, Daring Do claims to be allergic to spiders but turns out to be afraid of them rather than allergic to them. In Applejack and the Honest-to-Goodness Switcheroo, Big McIntosh is stated to be allergic to giant funflowers.

Blue flu

Discord's fake blue flu.

In Three's A Crowd, Discord fakes having come down with blue flu due to inadequate "hoof and claw washing" to get Twilight Sparkle and Princess Cadance to care for him as part of an elaborate prank. Among his faked symptoms are cerulean-hued skin and fur, and sneezing that sends the afflicted flying backwards; he additionally casts a random spell on any nearby object whenever he sneezes, such as burning up a tree's leaves in blue flames or blowing away an entire house. Discord claims the disease is highly contagious as Applejack and Rarity become afflicted after he sneezes on them, turning their coats blue within seconds. According to Discord, besides dozens of outlandish treatments, the blue flu can be cured with a magical soothing elixir brewed from a gargantuan "exquisite magic flower" that grows on a hill at the edge of Equestria, picked as it drops its petals at sunset. In My Little Pony: Friendship is Magic Issue #58, Twilight mentions blue flu as one of the diseases that the Magenta Bloom could potentially cure. It is also mentioned in My Little Pony: Legends of Magic Issue #6 that Mage Meadowbrook cured the blue flu in Salt Lick City.

Cleft teeth

Cleft teeth.

Flim mentions bridle-bit cleft during Flim Flam Miracle Curative Tonic in Leap of Faith as he inspects a pony with misaligned teeth.

Cold

Stallion suffering from a bad case of cold.

In Winter Wrap Up, Spike gets a cold after falling into icy water; his only noticeable symptom is sneezing. During the song in Hearts and Hooves Day, Sweetie Belle remarks that one of Cheerilee's potential suitors has "a terrible cold"; the pony has a reddened nose, blood-shot eyes, a thermometer in his mouth, and a hot-water bottle on his head. In Hallmark's My Little Pony Personalized Book [Child's first name] and the Pony Parade A Book Made Especially for You by [From], Rainbow Dash has a cold.^{​[​specify​]​}

Collective amnesia

The librarian Amethyst Maresbury, who can't remember where she works.

Applejack describes the Crystal Ponies' memory loss in The Crystal Empire - Part 1 as "some kinda collective amnesia." Twilight Sparkle and her friends seek out more information about the Crystal Empire so they can use the Crystal Ponies' magic to protect the empire, but find that they don't remember anything. The Crystal Pony that Twilight interviews can't remember anything before King Sombra came to power, and says that although they've been gone a thousand years, Sombra's rule "feels like it was just yesterday." Once the interviews prove fruitless, the ponies head to the library, where they meet a librarian pony who can't remember where the history section is or whether she even works at the library. The ponies find a history book which contains the information they seek and decide to hold a Crystal Faire to "renew the spirit of love and unity in the empire so they could protect it from harm," according to the book Twilight reads.

The Crystal Faire does jog the Crystal Ponies' memories and they recall the Crystal Heart. The librarian remembers that she really does work at the library. By the end of the episode, the Crystal Ponies even manage to recognize that the replacement Crystal Heart that Twilight fashioned isn't the real Crystal Heart, but the real Crystal Heart is eventually restored and the Crystal Ponies' magic protects the Crystal Empire once again.

Corruption

Nightmare Moon is born.

Trixie and corruption? Oh my...

In Friendship is Magic, part 1, Nightmare Moon is stated to be a corrupted form of Princess Luna, formed from her bitterness and jealousy toward her older sister Princess Celestia. More detail about this is revealed in the My Little Pony: Friendship is Magic Issue #5 story, and Luna's transformation into Nightmare Moon is shown in a flashback in Princess Twilight Sparkle - Part 1.

The Alicorn Amulet in Magic Duel blesses the wearer with enhanced magical powers but also "corrupts" the user, according to a book that the main characters find. Trixie, who possesses the amulet and uses it to take control of Ponyville, becomes more and more tyrannical and bitter as she continues to rely on its power. Since the amulet has a lock that prevents anyone other than the user from taking it off, Twilight Sparkle tricks Trixie into removing the Alicorn Amulet by pretending she possesses an even stronger amulet. The aura color of Trixie's magic, which was red before, turns back to pink, and her eyes no longer glow red from the influence of the amulet.

In Inspiration Manifestation, Rarity appears corrupted by a creativity spell from an enchanted spell book Spike finds in the Castle of the Two Sisters. Similarly to the Alicorn Amulet, Rarity becomes increasingly dependent on the book. Her magic aura also changes from light blue to a vivid green color, with her eyes glowing the same green whenever she uses the book's magic.

Croup

Discord with the croup.

Discord mentions he may have the croup on top of his faked blue flu during his song in Three's A Crowd, breaking out into flower-shaped spots as he does, and requests a vat of pumpkin soup, silk scarves, warm milk, and pastries from Abyssinia for treatment. In My Little Pony: Friendship is Magic Issue #58, Twilight mentions that the Magenta Bloom could cure "juvenile croup".

Cutie pox

One of the diagrams accompanying the entry in Perplexing Pony Plagues.

"Cutie pox" is featured in the eponymous episode The Cutie Pox, which Twilight Sparkle describes from a book: "This puzzling pony plague afflicted a population of ponies back in the Paleopony Period! Random cutie marks appeared all over the ponies' bodies, causing them to perform all the talents that came with them! The cause of the breakout was never discovered, and the cutie pox disappeared as mysteriously as they arrived!" Apple Bloom contracts cutie pox in the episode after an overdose of Heart's Desire plant petals. The pox is cured by the flower that grows from the Seeds of Truth supplied by Zecora, which sprout only in the presence of a truthful confession.

Cutie unmarking

Cutie unmarked ponies.

In The Cutie Map - Part 1 and Part 2, Applejack, Double Diamond, Fluttershy, Night Glider, Party Favor, Pinkie Pie, Rainbow Dash, Rarity, Sugar Belle, Twilight Sparkle, and numerous other ponies' cutie marks are removed by Starlight Glimmer and replaced by equal signs. Night Glider refers to this as the "cutie unmarking." Some ponies with this also exhibit losing color in their coats, shorter manes and tails, and rather phony, creepy, and exaggerated smiles. As an additional effect, the equal sign that replaces their cutie mark actively dampens a pony's individuality, and more specifically their special talent associated with their cutie mark.

Dementia

In Power Ponies, the Mane-iac jokes that "dementia must be a side-effect of prolonged exposure to the Hairspray Ray of Doom."

Feather flu

A number of ponies contract feather flu in Hurricane Fluttershy. Initially, Rainbow Dash accuses Thunderlane of trying to get out of setting a new tornado speed record with all the other Pegasus ponies when she hears coughing. Afterward, the pony who was standing behind Thunderlane, Blossomforth, coughs too. Rainbow Dash lists off at least seven other Pegasi who contracted the flu, with Thunderlane said to be at the hospital. At one point Twilight Sparkle sprays Thunderlane with an aerosol can of an unspecified substance to create a "germ-free environment."

Fur blight

A hairless rump.

Flim mentions the Clydesdale fur blight during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd a picture of a pony with hairless hindquarters. Fur blight is also mentioned by Zecora in A Health of Information.

Gallop plop

Coco Crusoe with short front legs.

Flam mentions gallop plop during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd Coco Crusoe with short front legs.

Greed-induced bigness

Grown Spike rampaging.

In Secret of My Excess, after Spike begins hoarding objects and having sudden and dramatic growth spurts, Zecora explains that Spike's greed is making him grow "into a monster." At the end of the episode he returns to normal after Rarity reminds him of his act of generosity towards her when he gave her a gem he had been been saving to eat on his birthday. This affliction is implied to be exclusive to dragons, and a natural part of their biology as opposed to something that Spike contracted. The affliction is mentioned by Smolder in Molt Down.

Hay fever

In The Cutie Pox, Twilight Sparkle mentions that she had been reading about "unusual equine illnesses" in a book entitled 'Perplexing Pony Plagues'. One of the illnesses she mentions is Hay Fever, though she gives no information about it. It is also mentioned in Leap of Faith by Flim and Flam as one illness that their tonic can allegedly cure.

Hearing loss

In The Mysterious Mare Do Well, Granny Smith briefly uses an ear trumpet indicating that she is hard of hearing. In Putting Your Hoof Down, "Geri" also uses an ear trumpet, and Apple Rose uses one in Grannies Gone Wild. In Molt Down, Rarity briefly goes deaf from the effects of phoenix feathers.

Hoof-and-mouth disease

Pinkie Pie mentions hoof-and-mouth disease during her song in Over a Barrel.

Hoof cough

Zecora mentions hoof cough in A Health of Information.

Hooferia

A too-short pony.

Flam mentions hooferia during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd a picture of a pony of considerably short stature. It appears similar to real-world dwarfism.

Horsentery

A tall bony pony.

Flam mentions horsentery during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd a picture of a pony with a tall and bony body structure. Its name is similar to a real disorder called dysentery.

Horsey hives

A sick group of foals.

In A Flurry of Emotions, several foals in Cheerilee's class become stricken with horsey hives and hospitalized. The disease takes a form of a chickenpox-like skin rash. In real life, hives are a burning or stinging skin rash usually caused by infection or an allergic reaction.

Hypnosis/mind control

See also: Changeling infection

Applejack falling under Discord's spell.

In The Return of Harmony Part 1, Discord hypnotizes each of Twilight's friends, turning their coats and manes gray and causing them to behave conversely to how they normally do. Applejack becomes a compulsive liar, Pinkie Pie becomes cold and bitter, Rarity becomes greedy, Fluttershy becomes an oppressive bully, and Rainbow Dash becomes disloyal. Twilight returns them to normal with a memory spell in The Return of Harmony Part 2.

Bridesmaids under changeling control.

The changeling Queen Chrysalis in the form of Princess Cadance casts a spell on Shining Armor in A Canterlot Wedding - Part 1. In the following episode, A Canterlot Wedding - Part 2, the ponies Shining Armor, Twinkleshine, Minuette, and Lyra Heartstrings are all under changeling control, wherein their eyes become green and glow. Later in the episode, the real Cadance uses her own magic to free Shining Armor.

In The Crystal Empire - Part 2, Twilight and Spike are hypnotized when King Sombra's magic door makes them confront their worst fears.

In The Cutie Re-Mark - Part 1, in an alternate timeline created by Starlight Glimmer, King Sombra forces the Crystal Ponies to fight in a war for him by using mind-controlling helmets.

In Every Little Thing She Does, Starlight Glimmer mind-controls her friends using the Fiducia Compelus spell in order to complete several friendship lessons at once. In their hypnotized state, the ponies have shrunken pupils with faded colors and speak mechanically.

In My Little Pony Equestria Girls, Sunset Shimmer uses the magic of the element of magic to bring the students of Canterlot High School under her control. The affected students' eyes turn pale green and they moan like zombies.

In My Little Pony Equestria Girls: Rainbow Rocks, the Dazzlings use their siren voices to sway the minds of everyone at Canterlot High School.

In My Little Pony: Friendship is Magic Issue #23, the ponies of Ponyville and Spike are hypnotized by the singing of a kelpie named Cassie. The Mane Six's pets, immune to the spell's effect, form a plan to stop the kelpie and release the ponies from her spell.

In My Little Pony: Friendship is Magic Issue #32, Twilight hypnotizes Fluttershy into becoming Flutterbat again.

In My Little Pony: Friendship is Magic Issue #48, Accord – Discord transformed by an astronomical event – brainwashes ponies and forces them to share a common mindset in order to bring "order" to Equestria.

Irrational fears

Ms. Peachbottom having a panic attack.

Ms. Peachbottom, who is mistaken for the Equestria Games Inspector in the episode Games Ponies Play, becomes frightened when entering the Crystal Palace because of the high ceilings (altocelarophobia) and smaller areas (claustrophobia). Throughout the episode, she tries to get outside of the palace and ends up wrecking the crystal stadium and almost runs right out of the Crystal Empire with a vase on her head.

Fluttershy suffers from a fear of heights in Dragonshy and stage fright/performance anxiety in several episodes, most notably Hurricane Fluttershy and Filli Vanilli. While some of this is rooted to the bullying she received at flight camp, they remain as everyday burdens to her. In Equestria Games, Spike suffers a similar fear from Fluttershy's, as depicted of feeling overwhelmed by a sheer number of ponies in the stadium. Tender Taps also suffers the same fear as both Spike and Fluttershy, as he's afraid to perform in front of an audience with his tap-dancing talent. Twilight Sparkle suffers from a fear of quesadillas in Party Pooped, and her human counterpart suffers from performance anxiety in My Little Pony Equestria Girls: Friendship Games during the archery portion of the Tri-Cross Relay.

Kennel cough

In Yakity-Sax, Fluttershy believes that one of Cerberus' heads has kennel cough. In real-life, kennel cough is a respiratory infection that affects dogs.

King Sombra's curse

Harmful crystals encrusting Shining Armor's horn.

In The Crystal Empire - Part 1, Shining Armor escapes from King Sombra's attack at the cost of having shadow crystals being grown on his horn which nullify the use of unicorn magic. It's only when the magic of the Crystal Heart is restored in The Crystal Empire - Part 2 that Shining Armor is cured. In My Little Pony: Friendship is Magic Issue #35, Sombra seals Twilight's magic. Princess Cadance's magic is also sealed in Issue #37.

Mane and tail loss

A pony with mane loss.

Flim mentions mane loss during Flim Flam Miracle Curative Tonic in Leap of Faith as he and Flam point out ponies in the crowd with bald (or balding) manes and tails. In It Isn't the Mane Thing About You, Rarity also mentions "mare pattern baldness."

Molting

Spike goes through the process of molting or "the molt" in Molt Down. According to Smolder, the symptoms include rather itchy stone scales, powerful flaming belches, and the uncontrollable volume of a dragon's voice. A dragon going through molt also produces a powerful odor that attracts predators, while the process in general causes dragon families to expel members going through the molt.

Pastelus coloritis

Capper makes up the disease pastelus coloritis in My Little Pony The Movie to steer the potential Klugetown residents from purchasing the Mane Six and Spike. According to him, those infected get covered with purple splotches and "parts will fall off", and will also result in death.

Petrification

See also: Gem Hoof

Twilight Sparkle turned to stone.

A cockatrice petrifies Twilight Sparkle and Elizabeak in the episode Stare Master. Fluttershy tries to warn the Cutie Mark Crusaders to never look one in the eye; later she confronts the cockatrice, which manages to partially turn her into stone, but using the Stare, she cows the cockatrice into turning Twilight and the chicken back to normal, and the stone that was partially encasing her shatters. Twilight does not retain any memory of her time spent petrified, as she openly admits to the overjoyed Cutie Mark Crusaders and to Fluttershy.

At the beginning of the episode The Return of Harmony Part 1, Discord, having been turned to stone by Princess Celestia and Princess Luna using the Elements of Harmony long beforehand, escapes after the Cutie Mark Crusaders get into a fight in front of his stone form. Celestia explains that the spell to keep Discord contained broke due to her and Luna no longer being connected to the Elements. At the end of the episode The Return of Harmony Part 2, the Mane Six use the Elements to turn Discord back to stone.

In the third season episode Keep Calm and Flutter On the effects of petrification on the victim are loosely explored upon. After the Mane Six use the Elements of Harmony to release Discord from his imprisonment the latter reveals to them that he had been listening in on Princess Celestia's idea of reforming him. Discord then reveals to Twilight Sparkle that while he was still petrified he had retained his sense of hearing. However, due to the fact that he could not move his body it made "rolling [his] eyes a challenge." It should be noted that it is unclear whether petrification in the case of the cockatrice and Discord's petrification via the Elements of Harmony are connected.

In the fourth season episode, Princess Twilight Sparkle - Part 2, Discord's petrification long beforehand is shown.

In My Little Pony The Movie, Tempest Shadow turns Princesses Cadance, Celestia, and Luna—as well as Derpy—into obsidian statues. At the end of the film, both the Storm King and Tempest are also turned to obsidian. While the King falls to the ground and crumbles to pieces, Twilight saves Tempest and restores her with the Staff of Sarconas and restores all the Princesses, Derpy and all of Canterlot.

In My Little Pony: FIENDship is Magic Issue #1, Sombra turns Princess Amore into a black crystal statue and shatters her. He also turns Princess Celestia and Princess Luna to stone in My Little Pony: Friendship is Magic Issue #35 and Shining Armor in Issue #37.

Poison joke

Don't walk on the grass.

Poison joke, which appears in the episode Bridle Gossip, is a magical plant that causes ridicule-inducing afflictions on the Mane Six who come into contact with it. In the episode, the ponies accidentally stumble into a large patch of poison joke despite warnings from Zecora, which are misconstrued as threats. The plant has large leaves with a bulb with several petals sticking out of the center, each bulb sporting a few stamen. The entire plant is blue, including leaves and stalk, with dark streaks running over it in a design.

Like its namesake, poison oak, it affects the ponies after they merely come into contact with it, but as described by Zecora, the plant does not poison its victims; rather, it plays practical jokes, which manifest as physical afflictions. The jokes in the episode magically match the victim's personality and traits. Spike also comes up with nicknames for the Mane Six's infections.

Fluttershy reciting Pinkie Pie's song, and the poison joke's effect on Pinkie.

In the episode, the ponies are afflicted with the following:

• Twilight Sparkle's horn becomes wobbly, soft and covered in blue spots. Spike gives her the nickname Twilight Flopple.
• Rainbow Dash's wings become inverted, being upside down and on her lower sides, making her fly funny and crash constantly. Spike's nickname for her is Rainbow Crash.
• Applejack shrinks down to a tiny size and can fit on a pony's hoof. Spike gives Apple Teeny as a nickname for her.
• Rarity's mane, coat, and tail become frizzled, very long, and mop-like. Spike nicknames her Hairity.
• Pinkie Pie's tongue becomes swollen and covered in blue spots, making her speak unintelligibly. Spike calls her Spitty Pie.
• Fluttershy's voice deepens into that of a stallion with a deep and masculine voice, provided by Blu Mankuma in S1E9 and Alvin Sanders and Marcus Mosley in S4E14. Spike gives the nickname Flutterguy for her.

The effects of poison joke are eventually cured when the ponies take an herbal bath for which the recipe is found in a book called Supernaturals: Natural Remedies and Cure-Alls That Are Simply Super, which Twilight initially ignored in the episode because of the first part of its title. Twilight told Spike when she saw that book, "This book is just a bunch of hooey!" but the book did indeed contain the cure.

In Filli Vanilli, Zecora reveals that poison joke effects can be deliberately triggered in a controlled manner by the use of a potion using the blossoms as an ingredient. She then uses this potion on Fluttershy so she can regain her deep voice of Flutterguy so she can use her deep singing voice to help out Big McIntosh when he loses his voice and becomes unable to sing for the Pony Tones.

In Daring Do and the Eternal Flower, Ahuizotl mistakes a poison joke flower for the Eternal Flower and shrinks down to the size of a mouse.

Poisoning

In early September 2016, Jim Miller said in a Twitter conversation, "What in over 100 episodes has ever given you the idea we might have a story involving POISONING?"

Food poisoning

Ponies suffering from food poisoning.

Some ponies suffer from food poisoning in Applebuck Season when Pinkie Pie accidentally serves "baked bads" after Applejack's sleep-deprived attempts to help with muffin baking go awry. Nurse Redheart and "Nurse Tenderheart" tend to a number of ponies who are seen squirming and writhing on their beds, many of whom are green-faced and some of whom vomit.

Love poisoning

Big Mac and Cheerilee under the influence.

A love potion is created in Hearts and Hooves Day by the Cutie Mark Crusaders and administered to Cheerilee and Big McIntosh. The Crusaders borrow a book from Twilight Sparkle and use a recipe from it to create a love potion, mixing "a tuft of cloud" and a "bright rainbow's glow" and stirring with a Pegasus feather. They trick Cheerilee and Big McIntosh into drinking it, and the two become deeply infatuated with each other. The Crusaders later discover that the drink is actually a love poison, and it makes ponies so "lost in each other's eyes" that they can't do anything else. The antidote is to keep the affected ponies "from looking into each other's eyes for one full hour," which, with much effort, they succeed in doing, breaking the spell.

Pony pox

See also: Pony flu

Fluttershy with a fake pony pox.

Fluttershy pretends to be afflicted with pony pox in Hurricane Fluttershy in an attempt to avoid Rainbow Dash's recruitment efforts toward setting a new tornado speed record. Fluttershy's faked symptoms include sneezing, coughing, and being covered in red spots. Rainbow Dash "cures" Fluttershy by dousing her with water, causing the fake red spots to wash off. Pony pox is also mentioned in My Little Pony: Legends of Magic Issue #6.

Rabies

Applejack addresses plunderseed plants as "rabid rhododendrons" in Princess Twilight Sparkle - Part 2.

The reins

Noteworthy with a blue tongue.

Flim mentions the reins during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd a picture of a pony with an irritated and blue tongue.

Saunter sitz

Cherry Berry with short hind legs.

Flam mentions saunter sitz during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd Cherry Berry with short hind legs.

Snifflitis

In Yakity-Sax, Fluttershy believes that two of Cerberus' heads have snifflitis.

The spurs

Infected hind legs.

Flim mentions the spurs during Flim Flam Miracle Curative Tonic in Leap of Faith as he shows the crowd a picture of a pony's infected hind legs.

Stomach ache

Spike suffering from stomach ache.

In Dragonshy, Fluttershy asks Angel to eat his carrot at a slower pace to prevent him from getting a "tummy ache." Spike is eating ice-cream throughout the episode It's About Time, eventually resulting in a stomach ache. In Three's A Crowd, Discord mentions "[his] stomach's feeling crummy" as a symptom of his faked blue flu. In the episode Maud Pie, Pinkie Pie's friends get stomach aches from taste-testing her various rock candy recipes. In The Cutie Map - Part 1, Pinkie Pie gets a stomach ache from eating a dozen poorly-made muffins.

Swamp Fever

The stages of Swamp Fever.

In A Health of Information, Zecora comes down with Swamp Fever after being exposed to a poisonous swamp flower. Its symptoms include orange spots, coughing bubbles, sneezing bolts of lightning, and confusion. In the disease's final stage, the victim turns into a tree that grows the same poisonous flowers that spread it. Initially, Swamp Fever is believed to have no cure, but Mage Meadowbrook and later Fluttershy discover the cure to be flash bee honey.

In real-life, "swamp fever" is another name for equine infectious anemia, a horse disease that may result in death.

Swelling

A pony with swelled-up hooves.

Flim mentions forms of swelling during Flim Flam Miracle Curative Tonic in Leap of Faith as he inspects ponies with swollen hooves and hindquarters.

Tatzl-flu

Discord with real tatzl-flu.

At the end of Three's A Crowd, a Tatzlwurm sneezes on Discord, causing him to turn green with spots. Unlike Discord's faked blue flu earlier, this illness is real, and it leads to him being quarantined in a plastic bubble in Fluttershy's cottage. The Curse of the Statuettes names tatzl-flu.

Tonsillitis

Sick tonsils.

Flam mentions tonsillitis during Flim Flam Miracle Curative Tonic in Leap of Faith as he points out a pony in the crowd with inflamed and spotted tonsils.

The trots

In The Cutie Pox, Twilight mentions that she had been reading about "unusual equine illnesses" in a book entitled 'Perplexing Pony Plagues'. One of the illnesses she mentions is "the trots," though no details are mentioned. In the real world, the trots are simply known as a case of very bad diarrhea.

Voice loss

Big Mac struggling to talk.

In Filli Vanilli, Big McIntosh loses his voice after a turkey call competition and becomes unable to sing for the Pony Tones. In a German comic, Pinkie Pie overexerts herself for the June dance, making her voice become very soft. Fluttershy makes some herbal tea to help heal it.

Zombification

Zombies in Friendship is Magic Issue #16.

In Bridle Gossip, when Twilight and Spike find the streets of Ponyville empty in the middle in the day, Spike fears that there are zombie ponies around.

In 28 Pranks Later, Pinkie Pie organizes a prank with everyone in Ponyville to teach Rainbow Dash a lesson about her excessive pranking. Her prank involves everyone acting like zombies as a result of eating joke cookies and having their mouths and teeth coated in rainbow colors. These "zom-ponies" walk about slowly and have faded coat and mane colors, dilated eyes, speech limited mostly to low groans and moans, and an uncontrollable craving for cookies.

In My Little Pony: Friendship is Magic Issue #16, when Twilight, Pinkie, Rainbow Dash, and Rarity become trapped in an empty book world, Pinkie uses her imagination to create an epic fantasy world, and one of their obstacles is a horde of zombie ponies. These zombies more closely resemble traditional zombies, having rotted flesh and missing body parts.

Other depictions

IDW comics

Changeling infection

See also: Hypnosis/mind control

In the My Little Pony: Friendship is Magic Issue #1 story The Return of Queen Chrysalis, a number of ponies, including Silver Spoon, Bittersweet, Apple Bloom, Sweetie Belle, Scootaloo, Octavia Melody, Sweet Cream Scoops[sic], Lyra Heartstrings and DJ Pon-3, appear with bright blue eyes, tiny pupils and formless expressions. In Twilight's journal, the condition is described as being 'infected' by the changelings. In order to blend in with them, Pinkie Pie leads the other main characters into walking like zombies.

Ear infection

In My Little Pony: Friends Forever Issue #13, Sweetie Belle gets an ear infection that affects her balance and prevents her from visiting Manehattan.

Equine flu

See also: Pony flu

In My Little Pony: Friends Forever Issue #33, most of Cherry Jubilee's crew "is out with this stubborn equine flu", Sweet Apple Acres "already got hit with the flu earlier in the season", and most of Buffalo Bull's traveling Wild West show troupe "has come down with the equine flu"—Buffalo Bull "got a bad case of that flu." The name comes from equine influenza.

Fungus infection

In My Little Pony: Friends Forever Issue #21, the ponies of Ponyville and Zecora fall ill due to eating a batch of fungus-tainted hay. Those infected become covered in red spots and have uncontrollable sneezing fits. When Zecora becomes infected, she stops rhyming and speaks nonsensically.

Lichen infection

In My Little Pony: Friendship is Magic Issue #58, the ponies of Bridleberg fall ill due to a lichen contaminating the town's water supply. Those infected become covered in blue spots. Mage Meadowbrook eventually cures the town by decontaminating the water.

Nilson swamp frog infection

In My Little Pony: Legends of Magic Issue #6, the population of Mareidian becomes infected when Nilson swamp frogs contaminate their food supply with poisonous secretions from their skin. Those infected turn green with dark splotches on their coat and behave like zombies, only speaking in unintelligible groans.

Phoenix fever

In My Little Pony: Legends of Magic Issue #6, it is mentioned that Mage Meadowbrook cured phoenix fever in Fillydelphia.

Sapphire flu

In My Little Pony: Friends Forever Issue #21, Spike mentions having caught the sapphire flu the previous month. He worried about giving it to Twilight, but according to her, the flu can only be caught by dragons.

Storybooks

Comet Tail's Curse

See also: Magic#Comet Tail

Comet Tail's Curse is mentioned throughout the chapter book Starlight Glimmer and the Secret Suite. It is stated to be a curse that strips unicorns of their magic if they try to alter another wizard's magic and leave it incomplete. However, it is commonly believed to be imaginary.

Gem Hoof

See also: Petrification

Gem Hoof is featured in the chapter book Trixie and the Razzle-Dazzle Ruse. It is a curse that turns anything that the afflicted individual touches into gems. If left unchecked, the curse will eventually crystallize the cursed individual's body into a statue.

Inknorance

Inknorance, according to Twilight in the chapter book Princess Twilight Sparkle and the Forgotten Books of Autumn, is "[t]he magical affliction that affects books and effectively erases knowledge by darkening their pages".

Magazines

Gigantism

The Sparkle World story The Hero of Ponyville! involves Spike becoming gigantic; however, unlike what transpires in the episodes The Cutie Mark Chronicles and Secret of My Excess, Spike possesses his usual appearance, though on a larger scale. Twilight Sparkle refers to him as a "giant baby dragon" and attributes his enlargement to him brushing against a magic plant. Later in the story, Twilight bathes him with a magic cure and he shrinks to normal size.

Paralysis

In one of the German comics, Twilight Sparkle, Applejack, and Spike discover Pinkie Pie and Fluttershy appearing to be petrified. Twilight reads in a book that when ponies are looking forward to something so much that they can't take the anticipation, they might get paralyzed. She tells Applejack and Spike that the cure is a special cereal with a smell that calms them down so they can wake up, and that this cereal doesn't grow anywhere in Equestria, only being found beyond the Everfree Forest. After traveling to a barley field outside of Equestria, the three of them return to Ponyville with some of the barley and make a campfire with it, which wakes up the paralyzed ponies.

Pony flu

See also: Equine flu

See also: Pony pox

In the Sparkle World story Pony Flu!, Rainbow Dash has pony flu, which gives her itchy spots. A few days later, she has recovered.