Henna

One day we visited a farm near Rabat, and a wedding procession passed by. The wedding tent was across a field fenced by prickly pear, a cactus native to North America which reportedly made its way to Morocco during the sixteenth century. (The fruits of this plant are ripe now and sold from food carts in the medina and buckets beside rural roadways.) A gap in this green fence was closed by a brush gate, which was opened for us so we could cross the field to join the festivities. We walked around grazing sheep and toward the music. The wedding musicians were warming up the guests prior to the appearance of the bride, and the women were ululating, clapping, and occasionally dancing. Several women made a protective circle and then lifted their skirts to show the henna designs on their feet and lower legs.

The earliest written evidence of the use of henna in bridal adornment goes back to 2100 BCE, when it was associated with an Ugaritic legend about Baal and the fierce goddess Anath. It was grown and used in Spain from the ninth century to 1567, when it was banned by the Inquisition. But it is still widely used--by Jews, Christians, Muslims, Zoroastrians, Sikhs and Roma--across the region from India to Morocco, and in places where people from that region have migrated. My Roma grandfather wrote a beautiful short story about his grandmother's wedding day in Wales, describing the henna designs on her hands. Henna has been used for joyful occasions other than weddings, including battle victories, births, circumcision ceremonies and birthdays.

True henna comes from the plant known scientifically as Lawsonia inermis. The active ingredient is an organic compound called lawsone that, when it bonds to proteins in the skin, is responsible for the coloring effect. Lawsone is found in fresh henna leaves, especially in the petioles, and it is released by smashing the leaves with a mildly acidic liquid. The mash may be powdered and then mixed with lemon juice or strong tea six to twelve hours before use. Without this resting period, the lawsone might not be released and the coloring might not successful. The stain may be improved by adding essential oils (e.g. tea tree, eucalyptus or lavendar) with high levels of monoterpene alcohols. The paste must be made from fresh leaves and left on the skin for at least a few hours and preferably longer; to keep the paste from falling off during this time, a sugar-lemon mixture (or just sugar) may be used. Sometimes the designs are also loosely wrapped during this period. Old henna turns brown, but some dishonest artists use a green dye to make the mix look fresher--an understandable deception in a hot climate, perhaps, since henna spoils quickly if it isn't kept in a cool place and away from exposure to sunlight. But once henna is applied to the skin, steaming or warming may darken the stain. Alkalines hasten the darkening process. Soaps and chlorinated water may spoil the stain.

Improperly stored henna may be contaminated by Salmonella or other microbes. Premixed henna powders may contain adulterants, including silver nitrate, chromium, pyrogallol, carmine and/or orange dye, that are hazardous to your health; certain henna products for use in body art are thus banned by the US Food and Drug Administration(though it is approved for use in hair products). So-called "black henna" is not really henna at all, and caution is advised: It often causes an extreme allergic reaction, with blistering and permanent scarring. The blistering might not appear until three to twelve days after application. Sometimes "black henna" is mixed with gasoline, kerosene, benzene or other chemicals associated with risk of adult leukemia.

But properly grown and mixed henna seldom causes an allergic reaction or other health problems. Morocco is among the major growers and exporters in the world, along with India, Pakistan, Yemen, Egypt, Iran and the Sudan. During years with the requisite timing and amount of rainfall, plants may yield two or even three crops a year. Fine henna artists in Morocco, almost exclusively women, can earn good money with their skilled work. Henna is also used to dye wool and leather, for its color and also for its antifungal properties. In ancient times the henna plant was also used to make perfume, and there is a new commercial demand for this product.

I teach a class that integrates science with global studies, with a focus on sustainability issues. I look forward to teaching about the history, production and chemistry of henna, closing with a (legal) henna party.