Its healing virtues have been known since Antiquity. An ointment of aloe cured Alexander the Great, after being struck by an arrow when besieging the city of Gaza, about 330 BC. The wound became infected and the ointment healed it.
Aloe barbadensis Miller is a plant of the family Liliaceae, the order of Lilials (the lily is another well-known member). The succulent plant is optimized to resist dry, desertic conditions. The Aloe group has been rather successful, several hundred species belong to it.
During the healing of a wound, a cut for instance, a first step is formation of a kind of scaffolding, consisting of a granulation tissue produced simultaneously with elastin and collagen. This provisional network is made of oligomers, i.e., small-length polymers, of sugars, glycosaminoglycans and glycoproteins. The active component in aloe sap seems to also be glycoproteic.
Among Egyptians of Antiquity, the aloe plant served as a symbol of renewal. It was used in burial rites. It signified a continued existence in the World of the Dead. Planted around the pyramids and along the roads leading to the Valley of the Kings, it served as an offering to accompany a dead pharaoh on his trip to the other bank: when the aloe plant flowered, this was sign that the King had reached his ultimate destination.
My book, in French, Copal benjoin colophane … , Le Pommier, Paris, 2007, provides more information on aloe.