It depends which type of henna you use. You will need to be sure that your chosen product is safe, particularly if you’re applying henna as a skin dye in pregnancy.
Natural henna, derived solely from the plant, and with no added chemicals, is safe to use on your hair or on your skin. This type of henna is brown, and is harmless. It’s often suggested as an alternative if you want to avoid chemical hair dyes while you’re pregnant. It gives your hair a semi-permanent colour, and is available in a number of shades.
Natural henna for use as a skin dye is often mixed with lemon juice and essential oils. You may want to check that the oils used are safe in pregnancy. It takes more than several hours for the paste to work. It will leave an orange stain that goes brown, and which lasts between one week and three weeks.
Black henna, however, contains a dye called para-phenylenediamine (PPD), and this is not safe, because it can cause dermatitis and severe allergic reactions.
PPD is used safely as an ingredient in hair dyes. However, it is illegal under European rules to add PPD to products for direct use on the skin. Despite this, you may still come across black henna tattoos at holiday resorts or at festivals.
Black henna may cause you pain in the short term, and damage your skin in the long term. It may also sensitize you to other products containing PPD. This means you’ll have a greater risk of having an allergic reaction to products such as hair dyes in the future.
If you think you’ve had a black henna tattoo, and your skin is now itchy or painful, see a doctor immediately.
Always read the packet before using any henna products or dyes, so you know exactly what they contain, and take these precautions:
Check the product carefully to make sure it’s natural henna, particularly if you are using it for skin dye. Natural henna is pure brown, takes many hours to work, and lasts a few weeks. Black henna is jet black, works quickly, lasts about a week, and is not safe.
If you are at all unsure if the product is natural henna, don’t use it.
Bending over to apply henna can be uncomfortable if you have a bump. Stop what you’re doing if you feel dizzy, or if you become short of breath. You could ask a friend to help you to apply the henna quickly and efficiently.
Don’t be tempted to keep the room hot to get more out of the henna colour. Overheating can make you feel dizzy, and may raise your blood pressure.