Incubation - an ancient Egyptian sleep cure for medical ills

The British Museum is hosting until 27 November an outstanding exhibition on underwater

From the Ebers papyrus: US NLM/NIH

archaeology from sunken ancient cities on the Nile Delta (the lost cities of Thonis-Heracleion and Canopus).
The exhibition highlighted trade, cultural and religious exchange among old Mediterranean civilizations and in particular interchange between ancient Greece and ancient Egypt.  Examples  were featured of a major Hellenised Egyptian deities.
A fascinating element of the exhibition was discussion of a Temple for Incubation as a way to cure ills, the granite building long submerged in soft sands, its disappearance accelerated with the sands became liquid due to seismic activity. It is intriguing to note the siting of an important temple for incubation on the Nile delta, as the name for ancient Egypt was Kemet (‘km.t’) after black earth of the Nile Delta.
The aim of sleeping the night in the temple was to allow incubi - bad dreams - to carry away toxic humours as causes of illness and so heal the sufferers - in return for generous donations.
This practice reflected widespread tradition linking dreams to temples, and the release of dreams as a way to cure disease: the ancient culture of visits to oracular shrines (oracles) where a god could be consulted through an inspired priest – the most famous perhaps the Oracle at Delphi in Western mainland Greece. A common further method to consult a god was incubation: the inquirer would sleep in the temple holy place and be rewarded with an answer in a dream. This would then be interpreted by the priest with an often ambiguous answer.
Cures might also be delivered through a dream: for example at the oracle to Amphiaraus at Oropus in Attica, the temple to the god of medicine Asclepius at Epidaurus, the oracle of Dionysus at Amphicleia, and the oracle of Trophonius in Levadhia.
Ancient Egyptian medicine is considered to date at least to the 27th century B.C.E. to the time when the Old Kingdom physician and architect Imhotep was the Vizier of Djoser. Imhotep was later deified. A key belief was that disease could be caused by an angry god or an evil spirit. However the Egyptians of the time were pragmatic in formulated effective treatments.

Sources for ancient Egyptian scientific medical practices include the Papyrus on surgical trauma bought by Edwin Smith in 1862 and dating to ~1600 B.C.E and credited to the much earlier Imhotep; and the Papyrus dating to 1500 B.C bought by Georg Ebers in 1873 at Luxor. The latter papyrus includes more than 700 remedies and spells to be used to ward off disease-causing spirits.The ancient texts also describe dreams and how to interpret them.
Priests played a key role in prescription of how to live as a way to avoid disease.  There were healing sanctuaries affiliated to temples where physician-priests could prescribe for the healthy and treat patients.
Purification included special diets, ritualized bathing and removal of all body hair. The patient could also be required to maintain a specific diet including what were considered to be unclear fish and animals. Perhaps via or influencing Hippocratic sources, diet might include involving fava beans (now recognized now as a precipitate for anaemia in people deficient in the enzyme glucose-6-phosphate dehydrogenase, a genetic disorder common in the Eastern Mediterranean and in Sub-Saharan Africa).

More on sleep and the interpretation of dreams in Ancient Egypt. 
British Museum. The dream book.