The epidemic of sensitization to para-phenylenediamine will cause loss of client base for oxidative hair dye. Generalizing from the results of a broad UK sensitization assay of adolescents in 2014, 16% of adults in western industrialized nations are now sensitized to PPD; by the time they begin to gray in 2030, all of these people will be unable to use oxidative hair dye and other products containing coal tar derivatives and 7% may have reactions severe enough to require hospitalization.  Many with extreme PPD reactions were sensitized by ‘black henna’ temporary tattoos.   In East Africa the practice of decorating skin with PPD to create ‘black henna’ temporary tattoos has been popular since the 1970’s;   levels of sensitization are very high; Khartoum, Sudan, now has over 300 hospital admissions each year from high systemic exposure to PPD.   North Africa, the Arabian Peninsula, and South Asia, where people have used ‘black henna’ since the 1980’s also have a high rate of hospital admissions related to the health consequences of PPD exposure. 

The current severe +++ sensitization reactions and deaths being reported now have not been seen since the early 1900’s when PPD dyes for hair were not regulated at 6% PPD or lower.  Because of the high dye percentage and large body area applications of PPD in ‘black henna’, many people are sensitized to other diamine-related chemicals and must avoid the entire portfolio of cosmetic chemicals which have proceeded from the initial synthesis of aniline dyes in the mid1800s. Development and promotion of ‘safer oxidative’ hair formulas may result in more injuries as many people sensitized through ‘black henna’ temporary tattoos are cross sensitized to chemically similar compounds.

Substitution of PPD for safe traditional henna body art began in east Africa in the 1970’s when Bigen and Peacock home hair dye kits were marked in the region. This practice spread and became fashionable in Saudi Arabia, Egypt, Pakistan, and India by the early 1980’s.   Women used high PPD content black oxidative chemical hair dye powders for body art instead of henna because PPD makes black stains on skin quickly; the finely powdered chemical dye can be manipulated into more complex patterns than roughly sifted local henna.  These applications of PPD to skin were done on brides, their wedding guests, and for social celebrations. Many were sensitized by the first time their skin was painted with PPD; if they were not sensitized in the first application, subsequent celebrations with ‘black henna’ for Eids, Karva Chauth and Diwali sensitized them. Five or fewer applications of 10% PPD in a patch test will sensitize 100% of subjects;  ‘black henna’ contains 15% to 60% PPD.  Some were unaware PPD sensitization would affect their health in the future; others regarded the blisters that arose after application to be of little concern, regarded as “suffering for beauty.” They felt black patterns were more beautiful on darker skin as well as more convenient. As these women mature, they may decide to dye their hair with oxidative hair dye.  For these women, the hypersensitivity reaction can be severe; anaphylaxis may be fatal.  Forty women have died in recent years in Libya from PPD sensitization,  and officials have called for a ban on oxidative hair dye.  There has been a similar call in Egypt and the UK.  Khartoum  and Karachi  average hundreds of admissions to the main hospital per year from PPD sensitization.  There is a solution to this problem: at the first sign of sensitization, immediately transition the person to pure henna, cassia, and indigo from oxidative hair dye. They cannot be transitioned to compound henna or adulterated henna without risking a destructive chemical reaction between the metallic salts in compound henna and the activators in oxidative dye: hair may break, turn an unexpected color, or in the worst case, incinerate.

Having studied many countries’ approaches to the ‘black henna’ health problem, and having been a consultant for national and local health boards, I believe I can propose a workable solution to the problem. The solution requires expanding access to safe henna products and limiting access to high PPD content powders. The USA is the only nation I know of that presently prohibits the use of henna as body art and that prohibition has contributed to the rise of ‘black henna’ and para-phenylenediamine sensitization.  ‘Black henna’ is formulated with materials that can be freely purchased by any person who wishes to do so.  People are prohibited from purchasing a safe alternative. There are solutions to this problem, they are within the purview of the US FDA, and mostly require enforcement of regulations already in place, with some adjustments to insure a safe and culturally sensitive access to henna for the seven million Hindu and Muslim citizens in the USA, as well as innumerable enthusiasts.

Based on my doctoral research (1) I estimate that as of 2013, there have been 140,625,000 people severely sensitized to para-phenylenediamine in areas of tourism by 2013, and that the number continues to increase by 9,375,000 each year.  Many of these were children sensitized between 1997 and 2015, who will be a rising demographic of sensitized adults seeking to mask gray hair from 2010 to 2040.  A far larger number of women are sensitized to para-phenylenediamine through cultural use where safe, traditional henna was formerly used to celebrate marriage and religious holidays, and is now replaced by para-phenylenediamine, as black stains considered more modern and fashionable.  Attempts by governments to ban ‘black henna’ have largely been ineffective as the desire for fast, black temporary tattoos continues, and the patrons either do not know the risk, don’t believe they will be affected, or don’t consider the risk of injury to be significant. Enforcement of ‘black henna’ bans have rarely succeeded because of the availability of para-phenylenediamine and the seasonal, informal economies of the practitioners.