Henna is a plant that grows in arid regions such as the Middle East, North Africa and India. See Meet the Plant. Henna is a word derived from the Arabic and is used to refer to the plant, the paste which is made of this, the application process, the henna day prior to a traditional wedding, and the final adornment on the skin. Also the word mehndi is often used for this purpose; it is the Hindi (Indian) equivalent of the Arabic word henna.

Henna is applied in the form of a paste, usually by means of a henna cone or a syringe. I work with henna cones for applying henna. This cone can be compared with a piping bag that is used for decorating cakes, but slightly smaller. With this a freehand design is drawn on the skin. The duration of the application depends on the size and detail of a design and may range from 10 minutes for a small adornment, to 10 hours for a full bridal henna.

I always mix my henna myself. For this I use henna powder (brand: Amira or Aashiqa), lemon juice, powdered sugar, water and essential oils (lavender, cajeput or tea tree). The ingredients are added in the right proportions so that a smooth paste is formed. Toko Mehndi does not sell henna equipment, but if you'd want to get started yourself, here are some providers of good quality henna products: 
Hand of Fatima 
en Nafisha’s Henna Fashion

For the best results of your final henna there are a few things you can do to prepare.

Precare

It’s best to take a bath just before your henna appointment, because after the application it is important to avoid coming in contact with water for a while. While having your bath, also you could scrub the skin so that you remove the dead skin cells and the henna can get deeper into your skin. One day before your appointment, wax the part of your body where the henna is going to be, because even the smallest hairs can get in the way of smooth henna application. On the day of your henna appointment, do not use any body lotion, cream, body oil or other skin care products, as these will put a thin layer on the skin, giving the henna less of a chance to penetrate the skin

Depending on skin type, place on the body, pre- and after-care of the henna, a design remains visible for 1 to 2 weeks, and in rare cases even up to three weeks.

Aftercare
After the application, leave the henna paste on for approximately 8 hours. Shorter is also possible, but as a general rule, the longer you allow the henna paste to penetrate, the darker the final henna stain. After 8 hours, you gently scrape the dried paste off the skin. (If you don't want to dirty your fingernails, a bank card will do fine.) Never use soap and water to wash the henna off and avoid water anyway the first 24 hours. Henna is initially orange in colour, but oxidizes in a few days to a dark brown. To care for your skin and to keep your henna adornment as long as possible, you may rub it (especially before bathing) with pure coconut oil.

100% natural henna is safe to use as hair dye and for body adornment. As far as it is known, ingestion is not harmful either, but I do not recommend eating henna! People with the so called G6PD deficiency should avoid using henna. For them, the active dye from the henna plant (lawsone) is toxic. But for other people henna is a harmless substance and is even used in some countries to alleviate skin conditions such as eczema and psoriasis.

Henna is medically recognized as safe for pregnant women and their babies. Henna is even recommended during pregnancy as a safe alternative to synthetic products to dye hair. However, always be sure to use 100% natural henna without synthetic additives. For the Belly Henna I always use lavender oil in my henna paste, as of the three oils that I use, this is the softest to the skin and its pleasant fragrance provides additional relaxation during application of the Belly Henna.

Black henna does not exist. Products marketed as "black henna" therefore never consist of 100% natural henna. Usually what we deal with is a mixture of henna and PPD, para-phenylenediamine, a dye that stains the skin faster and darker than henna, but which is also very dangerous. PPD can cause severe and persistent skin conditions. PPD, however, is not the only substance that is used to make henna black. Other dyes (which are less or not harmful) are also used, but none of these dyes as quickly and stays as long as PPD. Therefore, be vigilent! Always ask for the ingredients of the henna before you use it yourself or let a henna artist apply it to you, especially if it is sold as so-called "black henna".

Nowadays you see that more and more "white henna" is offered. However, this has nothing to do with henna. The white body decoration may consist of different things, but is usually a body paint that is washable and otherwise often harmless.

You cannot just remove or wash off henna, because the dye from henna adheres to the outer skin layer. This outer layer of skin replaces itself every so often and this also makes your henna adornment slowly disappear. The duration of this process varies by person; this could be one week to four weeks. You can even slightly accelerate the process by scrubbing the skin, often doing the dishes or taking a nice long soaking, but there is no way to remove henna immediately. Also henna in hair and on nails has to grow out and cannot be washed off.

In principle, henna can be applied anywhere on the body, but it is not equally visible everywhere. Henna on the hands and soles, for example, gives a dark brown colour, on arms a lighter brown, but on your neck it is barely visible. The final stain colour of your henna adornment also depends on skin type and aftercare.