Garlic is a plant related to the onion, used as a food substance and for medicinal purposes. It's also used to ward off Dark creatures. In particular, vampires are known to be averse to the plant, as it can be fatal to them if ingested in large quantities.
Quirinus Quirrell's classroom, as well as his turban, were said to smell strongly of garlic, which many students believed was to protect against a vampire Quirrell had met on his travels. Fred and George Weasley were known to brandish cloves of garlic at Harry Potter during the 1992-1993 school year to poke fun at the fact that many of the students believed him to be the Heir of Slytherin. In the 1993-1994 school year, during a chance meeting at the statue in front of the One-Eyed Witch Passage, Neville Longbottom discussed a essay on vampires assigned by Professor Lupin with Harry Potter. He stated that he didn't understand "that thing about the garlic" at all all, wondering if they had to eat it. In 1995, a vampire was almost killed after an overdose of garlic bread, an event that made the Daily Prophet.
- Harry Potter and the Philosopher's Stone (Mentioned only)
- Harry Potter and the Chamber of Secrets
- Harry Potter and the Prisoner of Azkaban (Mentioned only)
- Harry Potter and the Order of the Phoenix (film) (Mentioned only)