EPIDEMIC OF PARA-PHENYLENEDIAMINE SENSITIZATION 53 cumulative expertise and assistance of all who went to the community bath (16). Now that people bathe privately, they are cut off from the group knowledge of the henna pro- cess. The chemistry of henna, indigo, and cassia hair dye is simple, but requires experi- ence to mix and apply, and adjustments by each person for optimal results. It is not possible to market henna successfully with brief, static instructions the consumer cannot be a passive recipient of goods. Marketing henna will require education and interaction with consumers. The subtleties of hair type, water supply, mixing times, and application time are each signifi cant variables unique to each consumer. These cannot be learned from brief, static instructions. Web 2.0, the change from static web pages to dynamic or user-generated content and the growth of social media can serve as a bridge among people who need to reconstruct community knowledge through shared experience. Combining the informa- tion transmission of hair dye methods from before the 20th century and using parallel methods through the “electronic village bath” creates a convivial educational and social support group for henna. Expert customer service engagement with clients through elec- tronic interactive media is crucial to the success of henna in the 21st century, just as visits to the village bath and learning from other bathers was crucial to successful henna out- comes in the previous 400 centuries. Using dynamic electronic support, we have success- fully transitioned over 50,000 severely sensitized people from oxidative hair dye to henna, indigo, and cassia in the last 3 years alone (17). For the cosmetic industry to recapture hair dye clients lost to PPD sensitization and tran- sition them to henna, a box of powder with one paragraph of written instructions will not be suffi cient. A commitment to long-term education of and engagement with clients will be as necessary as developing the product infrastructure. Re-educating stylists about how to incorporate henna into salons will be crucial. Engaging with stylists who have had to abandon their careers because of chemical sensitization, and establishing salons for “plant- only” technologies serving highly sensitized patrons would be ideal. If, in 2030, 16% of graying clientele cannot use oxidative hair dye, the establishment of an alternative should be not only economically viable but essential to growth of the hair dye industry. REFERENCES (1) V. Smith, S. Clark, and M. Wilkinson, Allergic contact dermatitis in children: Trends in allergens, 10 years on. A retrospective study of 500 children tested between 2005 and 2014 in one U.K. centre. British As- sociation of Dermatologists’ Annual Conference. Leeds Teaching Hospitals NHS Trust, Leeds, UK (2015). (2) Cosmetic, Toiletry & Perfumery Association director-general, Dr. Christopher Flower, and Dr. Anjali Mahto, spokesperson for the British Skin Foundation (2016). Henna techniques are best learned interactively and dynamically

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