"You need the hospital wing. There may be a certain amount of scarring, but if you take dittany immediately we might avoid even that...."
-- Snape to Draco after Harry hit him with the Sectumsempra spell (HBP24)
Dittany is a healing and restorative herb, one of the plants found in One Thousand Magical Herbs and Fungi (PS14, Pm:SB). It may be eaten raw or applied as a tincture to cure wounds, provided they are not too deep (Pm:SB). A mixture of powdered silver and dittany, when applied to a werewolf bite, will prevent the victim from bleeding to death but not cure them of lycanthropy (Pm). A sick baby may be cured with the application of dittany (TBB/WHP). Dittany can also be used to heal Doxy bites (JKR-W1).
- Newt Scamander used Dittany to treat the injured Zouwu from Circus Arcanus (CG).
- Harry researched dittany in One Thousand Magical Herbs and Fungi during his First Year as part of his Herbology homework (PS14).
- Draco was given dittany for his cuts when Harry attacked him with Sectumsempra (HBP24)
- Hermione's go-to healing potion is Essence of Dittany which she used on Ron's injuries when he splinched during apparition (DH14). She also used Dittany on Harry's wounds when he was burned by the Horcux on the chest, bitten by Nagini on the arm in Godric's Hollow (DH17), and to heal all their many injuries after the escape from the Gringotts vaults (DH27).
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Notes
When Hermione uses Dittany on Ron's splinch wound, smoke rises, which may be a reference to another name of Dictamus alba - "burning bush" or "gas plant." Dittany is covered with a volatile oil called "isoprene" that can easily catch fire. Another type known as "Dittany of Crete" has historic use as a medicinal herb and also an aphrodesiac (love potion). The goddess of love, Venus, healed the wounds of the hero Aeneas with a stalk of dittany in Virgil's Aeneid. The philosopher Aristotle wrote that when wild goats on the island of Crete were wounded with arrows, they would seek out dittany to heal the wound. source: Wikipedia