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 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 Order of the Phoenix (film) (Mentioned only)