In literature and cinema, the legend of Cleopatra frequently recurs. In antiquity, this queen of Egypt bathed in donkey's milk in order to keep her skin radiant and youthful. For this she needed at least 300 donkeys (and obviously many slaves.)
Biochemical analysis of donkey milk enables us to determine its precise dematalogical role. This milk contains lots of fatty acis and vitamins A, E and F. Thanks to this composition, the milk is effective for dry skin and wrinkles: it's a natural tensor, able to prevent skin from aging and also regenerate it.
Donkey milk was highly prized by ancient peoples. The Greeks considered it an excellent remedy, the Romans regarded it as a luxury drink. Hippocrates recommended it for all sorts of maladies : poisonings and snake bites, joint pains, wounds, etc...

Closer to human milk.
In the 19th century, and even at the beginning of the 20th, many people used it as a remedy. At that time, especially in Paris, many "donkey milk dairies" were established so that upperclass women could purchase the precious beverage. It was sold for more than 8 francs litre (and this before WWI). When it went out of fashion, these dairies turned to the production of milk for babies whose mothers couldn't nurse them. Thus the "Hôpital des Enfants Assistés" for many years kept a troop of donkeys; babies suckled directly from the donkeys' teats. By weighing the infant they determined that he drank between one and one and a half litres.

Doctor Parrot, who ran the nursery at the Hôpital des Enfants Assistés, describes in detail how it was done (from the Bulletin de l'Académie de médecine, 1882) : "The stables where the donkeys are kept are clean, healthy and well-aired; they open onto the nursing infants' dormitory. Treated gently, the donkey easily lets itself be suckled by the baby presented to it. Its teat is well adapted to the baby's mouth for latching on and sucking. The nurse sets on a stool to the right of the animal near its hindquarters. She supports the child's head with her left hand , with his body resting on her lap. With her right hand she presses the udder from time to time to help the milk to flow, especially if the baby is weak. The babies are nursed five times during the day and twice during the night. One donkey can feed 3 infants for 5 months."