Henna has been used for centuries as a natural way to dye hair. Henna comes from a plant and comes in several colors produced from different parts of the henna plant, or by adding different plants to it. An important difference between henna and chemical hair dyes is that henna does not alter the structure of the hair. Henna washes out gradually over time without revealing a huge color difference between the treated hair and the roots growing in. Henna cannot be used to make dark hair lighter, but it may add depth and shine to darker hair.
Put on a pair of plastic gloves. You will wear the gloves for testing process as well as the dying process. Using scissors, snip off a small amount of hair from your beard. This will be your test sample.
Test a small bit of the henna on a hair sample and on your skin before use. Mix a small amount of the henna powder and warm water with a plastic spoon to form a thick paste mixture in a plastic bowl. Coat the hair sample that you cut off, wrap it in plastic wrap and let it sit for the recommended time, usually an hour (see your henna package for specific instructions). Then put a dab of the henna on the inside of your elbow and cover that for the same amount of time. Rinse both with warm water. If the hair sample looks lighter than desired, you will want to leave the henna on longer when dying the beard, and if it looks darker, leave it in for a shorter time. Check the patch on your arm where you tried the henna. If you have no reaction in 24 hours, then proceed with your beard.
Wash your beard as you normally would, then towel dry. Use your fingers to put petroleum jelly on the skin around your beard.
Mix the henna with warm water in the plastic bowl with the plastic spoon. Start with 2 tablespoons of powder with 1 tablespoon of water until the mixture turns thick and soupy.
Use the stiff applicator brush to apply it to your beard as thoroughly as possible. Use plastic gloves while applying the henna.
Cover the area you dyed with plastic wrap. You may need to hold it on with your hand.
Wash the henna out of your beard with water. Dry as normal.
If your beard has more than 20 percent gray hair in it, a color test must be done before using the henna. Henna may stain your skin a bit, especially red hennas. The stain will disappear after a couple of washes. The FDA has approved henna as a hair dye but not as a skin cosmetic. These instructions have been for a basic, powder henna; however, each henna has its own directions that you should read fully.
Beware of black hennas, which may contain a chemical dye called paraphenylenediamine (PPD). PPD can cause permanent scaring and severe skin reactions. Always check that the henna uses only plants such as indigo for dark colors and always perform a skin test. You cannot bleach out or dye over henna. Your hair will turn green.