Spattergroit

• Type: Magical Ailment
• Symptoms: A severe rash of purple pustules, potential for significant disfigurement.
• Contagiousness: Believed to be highly contagious, justifying quarantine or avoidance of the afflicted person.

Spattergroit is a magical disease characterized by the victim breaking out in a covering of painful, purple pustules. The condition is considered highly unpleasant and can be disfiguring. When the Weasley family created a decoy of Ron Weasley suffering from the illness, the transfigured ghoul was described as being covered in these pustules, making for a convincing and repellent sight. The severity can apparently range, but a serious case is believed to be life-threatening, as Percy Weasley commented he had heard his brother was “at death's door with Spattergroit.”

As a magical ailment, Spattergroit's primary “property” is its contagiousness, which makes it a useful excuse for a person to remain in isolation for an extended period. Its existence is well-known enough in the wizarding world for it to be a plausible alibi. The disease's main “usage” in the narrative is as a carefully constructed deception by the Weasley family to protect Ron Weasley. They used the excuse of Ron having a long-term, contagious illness to explain his absence from Hogwarts during the 1997-1998 school year. This allowed Ron to accompany Harry Potter and Hermione Granger on their search for Voldemort's Horcruxes without arousing the suspicion of the Death Eater-controlled Ministry of Magic.

The disease is first mentioned in 1997 when Professor Horace Slocorn considers using it as an excuse to avoid attending the funeral of Aragog the Acromantula, stating, “Can't be too careful, you know. Could be Spattergroit.” This establishes it as a known and feared illness prior to its more significant use in the plot. Later that year, following the fall of the Ministry of Magic, the Weasley family put their plan into motion. They transfigured the family ghoul that lived in the attic of The Burrow to look like Ron, complete with a severe case of Spattergroit. The ruse was maintained for the better part of a year and was convincing enough to fool outsiders and even Percy Weasley upon his return to the family.

Spattergroit serves as a critical plot device in Harry Potter and the Deathly Hallows. It provides the official, in-universe explanation for Ron's absence from Hogwarts, thereby protecting both him and his family from the wrath of Voldemort and his followers. Without this alibi, Ron's disappearance would have confirmed the Weasley family's connection to Harry Potter and their allegiance to the Order of the Phoenix, placing them in immense danger. The cleverness of the ruse underscores the resourcefulness of Molly Weasley and the lengths to which the family would go to fight against Voldemort's regime.

• In the official Daily Prophet newsletters written by J.K. Rowling for the UK fan club in the early 2000s, it was mentioned that a charlatan was peddling a fake cure for Spattergroit. (J.K. Rowling, Daily Prophet newsletter)