The common onion does not occur in nature. It has been cultivated for at least 3,000 years, probably developed from the Central Asian onion, Allium oschaninii. The dry outer skin of the onion that protects the bulb is used for dyeing. Even when these skins are red, the colour produced on wool mordanted with alum is always yellow, since the red pigments in the skins, anthocyanins, are not effective dyestuffs.Historical Data
Onions' historical importance is obvious in that they are depicted in Egyptian tomb paintings more often than any other plant. Onions' medicinal and health promoting qualities were exploited over the ages. Alexander the Great fed onions to his troops to give them strength in battle. The onion is the most frequently mentioned yellow dyeplant in the literature and is also good for dyeing eggs. The lightfastness on wool and silk is very poor, however. Such a yellow fades, often within weeks in daylight, without being exposed to direct sunlight.
