text: In Egypt around 2000 BC, the juice of Ammi majus was rubbed on patches of vitiligo after which patients were encouraged to lie in the sun. In the 13th century, vitiligo was treated with a tincture of honey and the powdered seeds of a plant called "aatrillal", which was abundant in the Nile Valley. The plant has since been identified as A. majus, which contains significant amounts of both bergapten and methoxsalen, two psoralen derivatives well known for their photosensitizing effects.
  In the 1890s Niels Ryberg Finsen of Copenhagen developed a bulky phototherapy machine to treat skin diseases using UV light. In 1900, the French electrical engineer Gustave Trouvé miniaturized Finsen's machine with a series of portable light radiators to heal skin diseases such as lupus and epithelioma. Such machines have only been available in a chemically synthesized form since the 1970s.
  In the 1940s, Abdel Monem El Mofty from Cairo University Medical School used crystalline methoxsalen (8-methoxypsoralen, also called xanthotoxin) followed by sunlight exposure to treat vitiligo. This began the development of modern PUVA therapy for the treatment of vitiligo, psoriasis, and other diseases of the skin.