JOURNAL OF COSMETIC SCIENCE 70 Henna presently in the marketplace is coarsely sifted twigs and scraps often cling to hair through several washings. The dye content of henna decreases quickly when packaged in thin, single-walled cellophane envelopes. Henna, cassia, and indigo milling and sifting must be improved to 150 μm particle size to be acceptable to western consumers accus- tomed to easy-to-apply, easy-to-rinse hair dye. There must be no sand or plant debris in the leaf powder. Double-wall packaging is necessary for the powders to retain quality over several years. Indigo must be kept from moisture and freezing, or the dye will be spoiled. Henna must be kept under 32°C to maintain dye quality. Vacuum-packed henna, though it might seem to be an attractive way to preserve quality, adheres to itself and becomes barely breakable even with a hammer (Personal Experience). The Central Arid Zone Research Institute in Jodhpur, India, has conducted research on plant breeding, soils, and pests, enabling more reliable crops of higher quality. Improved milling and an improved supply chain has made Rajasthani henna cost more than henna from other countries (16). The supply is reliable and quality predictable, but the lawsone content varies from year to year. Based on my own lab testing and 25 years of experience, the highest lawsone content crops from Rajasthan occur during El Nino events when the plants are stressed by extreme heat and late onset of the monsoon. Lower lawsone contents in Rajasthani henna correlate with La Nina events. To obtain consistent lawsone content for marketing and formulation, more than one source will have to be developed to com- pensate for variation in crop quality. Other countries produce henna, but no other govern- ment has allocated resources to henna to the extent as has India. On the western side of the Thar Desert, henna from Pakistan can be of high quality and the milling is usually excellent. LUKE II examinations of henna show Pakistani henna can be grown adjacent to other crops unlike Sojat henna where the main henna district is monocropped. I have found pesticide blow-over from both tomato and cotton crops in Pakistani henna the amounts are negligible, but measurable. LUKE II tests of henna from the Sojat crops often reveal low levels of synthetic pyrethrin pesticide residue, probably from treating the castor semi-looper caterpillar (Achaea janata) that occasionally invades the monocrop (17), and occasional detectable DDT residue, probably drifted from mos- quito treatments of nearby habitation. Henna from India often has green dyed sand and other adulterants added (18). According to the independent certifi ed laboratory tests (Alkemist Labs, Costa Mesa, CA) and my personal experience with henna over the last 25 years, Yemen produces some of the highest dye content and cleanest henna I have never found pesticide residue in the LUKE II tests in the henna from Yemen. The milling from some producers is very fi ne though oth- ers have rough milling and sifting. At present the infrastructure in Yemen has been bro- ken by civil war and suppliers are presently unable to export to the United States. Henna Areas suitable for growing henna, and centers of commercial henna production, 2009.

EPIDEMIC OF p-PHENYLENEDIAMINE SENSITIZATION 71 is grown and milled from Iran but trade and banking restrictions have prevented direct importing into the United States for several years. Morocco has a reputation of perfectly sifted henna, but domestic production has fallen lower than domestic consumption levels Morocco presently imports henna from India, cultivating more profi table crops and the seasonal farm labor migrates to Europe. In Mauritania, henna is grown as a domestic and export product. The samples of Mauritania henna I have tested are coarsely sifted, but are otherwise good henna. The Nigerian henna samples that I have tested contain sand. Su- dan produces excellent henna, with high dye content and a more brownish tone than Iranian henna, but is coarsely sifted. All of the countries in the Sahel could be excellent henna producers, but the infrastructure necessary to raise henna production consistent with western market standard is not yet in place. EXPANDING COMMERCIAL HENNA PRODUCTION IN THE SAHEL The most promising area for expansion and improvement of henna production is the south- ern boundary of the Sahel. Rajasthan’s success with henna to secure farmland and soil at the eastern edge of the Thar Desert can be repeated in the “Green Wall” project, the in- ternational project to “green” the southern border of the Sahel, to reverse the Sahara’s southward progression and to stabilize farming communities across the area. Henna is indigenous to the region. A small henna tree with its deep, gnarling, and spreading root base can stay in the ground and for up to 50 years. Henna is often planted as a “living fence” to keep livestock and wildlife out of vegetable gardens (19). In addition, henna tolerates soil that has become salinized from irrigation and climate warming (20). Henna thrives in fi ne, sandy, well-drained soil hot, dry, sunny weather conditions promote higher law- sone content in leaves. In semi-arid areas with average annual precipitation of 250–450 mm, henna can be cultivated as a rain-fed crop (21). Leaf harvesting from the henna trees is most productive during the fi rst three decades, but henna plants that are not economically productive, even stumps, tenaciously hold soil in place acting as a living wall against desert encroachment and improving the land. Henna may be intercropped with legumes, further improving the soil (22). Henna leaves are harvested from the trees once or twice a year, and are a cash crop when all other crops fail from extreme weather events. No mechanical planting, harvesting, or any other fossil fuel–consuming equipment is necessary for tending henna a hoe, pruning knife, and gloves are all that is necessary for crop maintenance and harvest. The cultural association Areas where commercial henna cultivation can be expanded and tenacious henna root growth pattern.