- "We're going to put out the story that I'm seriously ill with spattergroit, which is why I can’t go back to school. If anyone comes calling to investigate, Mum or Dad can show them the ghoul in my bed, covered in pustules. Spattergroit’s really contagious, so they’re not going to want to go near him."
- —Ron Weasley[src]
Spattergroit was a highly-contagious wizarding disease caused by an infectious fungus.
Spattergroit caused the skin of those infected to break out in purple pustules. Once healed, these blisters could leave scars, particularly on the face. Sufferers were rendered unable to speak once the infection reached the uvula. The disease could leave people bed-ridden for several months.
Contact with individuals suffering from spattergroit was avoided as much as possible due to the extreme contagiousness of the disease. Parents with afflicted children pulled them out of school until they got better.
A massive outbreak of Cerebrumous Spattergroit was one of several things speculated to have been behind the mystery of why no one in the wizarding world could remember the Quidditch World Cup actually taking place in 1877.
Harry Potter first learned of spattergroit in 1995 when he visited Arthur Weasley in St Mungo's Hospital for Magical Maladies and Injuries. While heading for the hospital's tea room, a medieval Healer in a magical portrait diagnosed Ron with the disease, given the "unsightly blemishes" on his face. The portrait suggested that Ron "take the liver of a toad, bind it tight about his throat and stand naked by the full moon in a barrel of eels' eyes." Ron took this diagnosis with great offence, countering that the spots on his face were only freckles. It is unknown if the portrait's suggested treatment actually worked.
In 1997, Arthur, Fred and George Weasley transfigured the family ghoul and gave it purple pustules in order to make it look like Ron with the affliction. This ruse was concocted in order to explain Ron's absence from school. Hence, when he did not appear at Hogwarts for his seventh year, his family could claim that he was too ill to attend, due to the fact that attendance at school was mandatory for that year.
- Harry Potter and the Order of the Phoenix (First mentioned)
- Harry Potter and the Deathly Hallows (Mentioned only)
- Pottermore (Mentioned only)