Quantification of Lawsone and p-Phenylenediamine in Natural Henna Products for Hair Colouring Available in Poland.

Abstract

Background: Henna is a powdered plant material traditionally used for medicinal and cosmetic purposes in Asia and the Mediterranean region. In North America and Europe, however, it is only used to colour the hair and decorate the body. This colouring process is due to the action of the secondary metabolite lawsone, which enables henna to produce orange to red shades of colour. The final colour effect of the henna treatment on the hair depends on many factors, including the amount of lawsone in the product used. Unfortunately, there are also henna products on the market that contain the strong allergen para-phenylenediamine (PPD). Henna products whose manufacturers do not inform consumers about the addition of PPD are a particular problem.

Objectives: The aim of this study was therefore not only the qualitative and quantitative evaluation of lawsone but also of PPD in selected products offered for sale as henna.

Methods: Since HPLC assays are one of the most sensitive, rapid and reliable methods for the quality control of herbal raw materials, we developed and validated two independent HPLC methods with UV detection for both analytes.

Results and conclusions: We found that only about 60% of the tested cosmetic products were good quality natural products containing not < 0.5% lawsone (the range was between 0.5% and 1.0%). On the other hand, up to 36% of the henna samples contained PPD (the range was between 1% and 9%), and only three out of five of these products were properly labelled. Unfortunately, most of the henna used by Polish consumers comes from online retailers and can be shipped from different regions of the world. It is difficult to adequately control this market. Therefore, proper consumer education and awareness of the risk of PPD exposure when using henna could also be crucial for the prevention and management of PPD allergy.