Helichrysum, or immortelle, is one of the costliest oils and one of the few with a real reputation for bruises. Its signature compounds are the italidiones, a group of diketones found in almost nothing else.^[1] Neryl acetate makes up as much as two fifths and gives the honeyed, slightly tea-like smell. Studies credit the oil with calming inflammation and helping wounds close.^[2] Most of that work is in the dish or in animals rather than trials in people.^[2]