Henna Hair Dye
Henna is one of the oldest plant-based hair dyes known to mankind. Unlike most contemporary hair dyes, it doesn't contain any toxins or harsh chemicals, and it's generally a considerably cheaper product. It is also said to be GOOD for your hair, unlike some chemical dyes that MUST be used in conjunction with a good quality conditioner to keep your hair in good health.
But henna isn't simply henna any more. In fact today you can buy henna products that will color your hair different shades of red and brown. Having said this, be aware that products sold as "henna" that are said to just condition and strengthen your hair (so-called "neutral henna") are not derived from the same plant that produces henna hair dye. Henna is, by its very nature, a dye. It cannot be neutral or lack color.
So what exactly is henna? The short answer is that henna is a flowering plant (a small tree in fact), Lawsonia inermis that has been the source of dye since antiquity. Apart from its widespread use to color hair, dye from the henna plant is also used to color other materials (leather and wool for example) and to create tattoos in the skin of the human body. Lawsonia inermis (its botanical name) grows in tropical regions, and is native to parts of Africa, Asia and Australasia. So it's not surprising, knowing that henna has been used since antiquity, to discover that Cleopatra used it as a hair dye in Ancient Egypt.
While henna is generally considered to be a kind of "red" hair dye, the color of your natural hair will affect the resultant color you are likely to achieve. Unlike regular commercial dyes that give you a good indication of the color hair you will have after applying henna, you will need to be guided by fairly broad categories that range from orange and brown chestnut, to deep red burgundy and classic auburn.
Some companies also market blue-black henna hair dye powder, but to achieve this result, the product must be mixed with an indigo (blue) dye as well. Usually the henna is applied first, then, when this has dried, the indigo is applied on top. Then the whole lot is washed off. So-called "natural" henna powder will produce an orange-red hair color that will get darker and darker if the henna hair dye is used over time. Some people end up with an auburn color after they have used henna for a long time. Again it will depend on what your natural hair color is.
Nevertheless, henna is not a permanent hair coloring, but is rather considered to be semi-permanent. So if you don't continue to apply it, it will eventually wash out and you hair will return to its natural hue.
Some say that it was the highly acclaimed 19th century Italian opera singer, Adelina Patti, who first popularized the use of henna as a "modern" hair dye in Europe. More recently multiple Emmy Award-winning American actress and comedienne, Lucille Ball used it to color her hair when acting the character Lucy Ricardo in the early TV show I Love Lucy. As a result it became a hugely popular hair color treatment during the 1950s. Since then it's never gone completely out of fashion.
Like all hair dye products, you will find instructions on henna packaging that will explain exactly how to apply the dye. One aspect that may not be mentioned is that if you have dyed your hair using a regular chemical product, you should allow your chemically-colored hair to grow out before you switch to henna. If you don't, the chemicals that are already in your hair may react with the natural dye in henna, and you could end up with a color you may never have even envisaged. There's an even chance that it could be horrid.