JOURNAL OF COSMETIC SCIENCE 50 western consumers accustomed to easy-to-apply, easy-to-rinse dye. Henna, cassia, and indigo milling and sifting must be improved to 150-micron particle size there must be no sand, adulterants, additives, or plant debris in the leaf powder. Double wall packaging is necessary for the powders to remain quality over several years. Indigo must be kept from freezing, or the dye will be spoiled. Henna must be kept under 90°F to maintain dye quality. EXPANDING AND IMPROVING THE RESOURCE BASE Most of the henna currently in the marketplace at present is grown in the Sojat region of India about half of the annual crop is exported. India has improved henna milling facili- ties in Jodhpur and Faridabad. Henna sifted to western expectations of quality is avail- able, but the quality of the crop varies from year to year the highest lawsone content crops seem to coincide with El Nino events. To obtain consistent lawsone content for the market, more than one source will have to be developed to compensate for variation in annual crops. Sudan produces excellent henna, but more coarsely sifted than is acceptable. Yemen produces some of the highest dye content henna in the world, and the milling is good, but at present, the infrastructure in the country has been broken by civil war, and supplies are unreliable. Henna is available from Iran but trade restrictions have limited the supply to the United States for many years. All of the countries in the Sahel could be excellent henna producers, but the infrastructure of henna production to western market standard is not yet in place. Morocco and other North African countries have produced henna in the past, but have turned to more lucrative and modern agricultural products to serve the European market. The development of multiple henna-growing areas will pro- vide a more stable resource base. An expanded and improved market for henna, indigo, and cassia with investment in plant breeding and milling infrastructure could improve economic and political ties to these areas. If the global henna supply must be increased to meet rising demand or if other strains of henna are desired for varied characteristics, other growing areas should be developed. A henna tree must grow for 1 year before leaf harvesting can begin a henna tree can remain productive in the ground for up to 50 years. An initial investment in planting a henna crop can produce income for two generations. Indigo is grown and har- vested annually. Cassia obovata is a perennial in frost-free zones. Henna leaves contain 0.3–3% lawsone, 2-hydroxy-1,4-naphthoquinone. Since the law- sone content varies, high-performance liquid chromatography (HPLC) batch testing is crucial to predict the color outcome. The longer henna paste is kept moist in the hair, the more intermediate lawsone molecules will have the opportunity to migrate into the kera- tin 6 h generally is enough for maximum absorption of henna. Warmth facilitates a faster uptake. As more lawsone molecules migrate into the cuticle and bind with the keratin, the more saturated the color result will be. An HPLC test of powdered henna leaves generally shows 0.5–3% lawsone, a red-orange naphthoquinone molecule (11) which readily, harmlessly, binds with and stains keratin. The staining action is facilitated when henna leaf powder is mixed with a mildly acidic medium a pH 5.5 paste mix is ideal (12) to transform the precursor to the intermediate. The intermediate will bind to keratin via a Michael Addition creating a nonfading stable bond of the lawsone molecule with keratin. This red-orange stain can gradually oxidize to a brownish color by oxidation or contact with minerals commonly dissolved in tap water.

EPIDEMIC OF PARA-PHENYLENEDIAMINE SENSITIZATION 51 The lawsone precursor in the henna leaf is converted into the intermediate aglycone by mildly acidic hydrolysis. The aglycone intermediates will bind to keratin. Neither the precursor nor the fi nal lawsone will bind as effectively to keratin as the aglycone interme- diate. In mildly acidic henna paste at room temperature, the aglycone will become avail- able after about an 8-h soak, and remain at maximum content in the paste for 12–24 h, after which the percentage of the bindable aglycone form of the lawsone molecule will gradually diminish. Henna paste left out too long produces weak stains which shampoo out of hair. This transformation is gradual at room temperature, proceeding more quickly in warm conditions and slowing under cold conditions. When all of the unstable agly- cone precursors have transformed to the stable form of lawsone in about 1 week at room temperature, the demised henna paste will keratin a weak orange color that will not darken (14). The Michael Addition stain is permanent, and the color oxidizes to natural shades of red and auburn. After several days, the hair color matures and becomes very a stable color that does not fade even after daily shampoo for 10 years. Cassia obovata leaves contain chrysophanic acid (chysophanol), a golden yellow anthra- quinone molecule, chrysophanol (1,8-dihydroxy-3-methylanthraquinone). The cryso- phanic acid in cassia can dye pale or gray hair a golden wheat color, but the stain is not as permanent as henna. The dye is translucent and does not make dark hair a lighter color. Proportional formulations of cassia, henna, and indigo can yield a wide range of blonde, strawberry blonde, ash blonde, and pale brunette tones for pale or graying hair. Cassia powder, like henna, gives best results when mixed with a mildly acidic liquid and al- lowed the mix to rest overnight to release the dye. As with lawsone, only the intermediate molecule will bind permanently to keratin and not wash out. Vashma indigo is fermented and powdered form of indigo leaves, used with henna to cre- ate brunette and black hair dyes. Indigofera tinctoria leaves contain indican, a colorless molecule that is converted to indoxyl during alkaline fermentation. When indigo leaves are soaked in water and partially fermented, the indican molecule breaks into β-D-glucose Lawsone is produced by precursors in the henna leaf: the sequence of henna dye release and binding (13). Chrysophanic acid (1,8-dihydroxy-3-methylanthraquinone)