The first recorded user of henna as a hair dye was the Egyptian Queen Ses, mother of King Teta (Third Dynasty). The plant has always popularly been called Egyptian henna, although it is found abundantly also in Tunis, Arabia, Persia, India, and other tropical countries. It was commonly used by the inhabitants of all these countries to dye not only human hair but also the nails, the palms and soles of dancers, and the manes and tails of horses. Because all red shades of hair were out of favor for several centuries, and because the plant was obtained from foreign countries only with great difficulty, the use of henna died out in Europe. It was revived by the Spanish-born Italian singer, Adelina Patti (1843-1919), about the middle of the nineteenth century, and it was introduced into the United States when the great singer made her debut in New York in 1859. The dark purplish-red or so called mahogany shade she favored remained popular for decades.

The henna plant is a shrub, lawsonia alba Lam. or lawsonia inermis L., similar to the familiar privet. It bears small, fragrant, greenish-white flowers, but, as the only parts utilized for dye are the leaves and stems, the plants are frequently cut back. For infusions, used as rinses, the leaves are usually left whole, but in the more common commercial form of henna the leaves and stems are ground to a powder, about the color of dark mustard and with a characteristic earthy odor.

The active coloring principle in henna was called lawsone by Tommasi, who isolated it in 1916 and determined its chemical construction to be 2-hydroxy-1, 4-naphthoquinone, C₁₀H₆O₃. Further definitive work on henna and lawsone was done by H. E. Cox. The extract is an orange-red dye, readily soluble in water, dilute alkalies and acids. The true color can be seen best on white hair. Actually, its coppery, carrot-red shade is the same on all hair of any shade, but it seems to impart different colors because of variation in the basic shade. The color of henna is developed best in an acid medium (8,18,19).

The principal advantage offered by henna as a modern hair dye is that it is harmless to the system and causes no irritation of the skin. The disadvantages are that the shades it produces are not altogether natural. For keratin, henna acts as a substantive dye. A few applications impart a slight amount of color to the entire hair shaft, and depending on the original color of the hair, a whole range of reddish, “pure vegetable” shades—tomato, beet, egg plant—can be produced. In continued use, however, it seems to accumulate on the outside of the hair. If it is applied often enough, therefore, hair of any and all original shades can be brought to the same characteristic orange-red (10).