Amortenitia is an extremely powerful love potion which causes the effect of obsession or infatuation. The smell of the potion differs from person to person depending on what they find the most attractive.
It is used by mostly girls to attract the ones they like. It is also know to grow powerful the more it ages.
Harry Potter and The Half-Blood Prince
Ronald Weasley accidentally ate Romilda Vane's supposed to be chocolates for Harry Potter.