Afflictions and illnesses

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

Depiction in the series
In late March 2013, Meghan McCarthy was asked "ok do you know if their is an episode that talks about disabilites?" [sic] and answered "Yes." In early April 2013, she was asked by the same person "on what i said about disabilites is there a future episode or has there been one already been made?" [sic] and answered "One being made that will air in the future. :-) I’m very excited about it. It’s a very fun episode."

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, "Screw Loose" barks like a hound dog while chasing Rainbow Dash from the hospital.

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.

Cold
In Winter Wrap Up, Spike gets a cold after falling into cold 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.

Collective amnesia
Applejack describes the Crystal Ponies' memory loss in season three's opener as "some kind of 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 Fair 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 Fair does jog the Crystal Ponies' memories, they recall the Crystal Heart–and the librarian recalls 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
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.

Cutie pox
"Cutie pox" are featured in the eponymous episode The Cutie Pox, which Twilight describes from a book: "This puzzling pony plague afflicted a population of ponies back in the Paleopony period. Several random cutie marks appeared all over the ponies' bodies, causing them to be forced to perform, without stopping, all the talents that came with them. The cause of the breakout was never discovered, and the cutie marks 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.

Feather flu
A number of ponies contract feather flu in Hurricane Fluttershy. Initially Rainbow Dash accuses Thunderlane of trying to get of 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."

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 them green-faced; some of them vomit.

Greed-induced growth
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.

Hay fever
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 Hay Fever, though she gives no information about it.

Irrational fears
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 and smaller areas. 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.

Love poisoning
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 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 makes ponies so "lost in each other's eyes" that they can't do anything else, and that 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.

Petrification
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 Sparkle did not retaine 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 six main ponies 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 six main ponies 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.

Poison joke
Poison joke, which appears in the episode Bridle Gossip, is a magical plant that causes ridicule-inducing afflictions on the six main ponies 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.

In the episode, the ponies are afflicted with the following:
 * Twilight Sparkle's horn becomes wobbly, soft and covered in blue spots.
 * Rainbow Dash's wings become inverted, being upside down and on her lower sides, making her fly funny and crash constantly.
 * Applejack shrinks down to a tiny size and can fit on a pony's hoof.
 * Rarity's mane, coat, and tail become frizzled, very long, and mop-like.
 * Pinkie Pie's tongue becomes swollen and covered in blue spots, making her speak unintelligibly.
 * Fluttershy's voice deepens into that of a stallion with a deep and masculine voice, provided by Blu Mankuma.

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, "Spike, that book is just a load of hooey!" but that book did indeed contain the cure.

Allergies
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.

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.

King Sombra's curse
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.

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.

Changeling infection
In issue 1 of the IDW My Little Pony: Friendship is Magic comics, a number of ponies, including Silver Spoon, Apple Bloom, Sweetie Belle, Scootaloo, Octavia Melody, Sweetcream Scoops, 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.

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.

Weak voice
In another 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.