Mehandi (Henna), derived from the plant Lawsonia inermis, is one of the oldest natural dyes used for body art, hair coloring, and traditional medicinal applications. Beyond its cultural significance, henna represents an interesting example of applied organic chemistry, where naturally occurring molecules interact with biological tissues to produce long-lasting coloration. The primary coloring constituent of henna is Lawsone (2-hydroxy-1,4-naphthoquinone), a naphthoquinone compound responsible for the characteristic reddish-brown stain. When henna paste is applied to skin or hair, Lawsone penetrates the outer layers and reacts with amino groups present in keratin proteins through covalent bonding mechanisms, resulting in stable dye-protein complexes. The staining intensity is influenced by factors such as pH, temperature, oxidation, and the presence of terpenes from essential oils. Acidic conditions facilitate dye release, while heat and oxidation enhance color development and permanence. This article discusses the chemical composition of henna, the molecular mechanism of dye formation, and the roles of various paste ingredients in improving staining efficiency. Furthermore, a comparison between natural henna and synthetic black henna containing para-phenylenediamine (PPD) is presented, highlighting the chemical basis of allergic reactions and associated health risks. The review also examines the applications of henna in cosmetics, hair dyes, textile coloration, and medicinal formulations. Through an exploration of its chemistry, henna emerges as a sustainable, environmentally friendly, and biologically compatible alternative to many synthetic dyes. Understanding the molecular interactions involved in henna staining provides valuable insights into natural dye chemistry while emphasizing the importance of safe and eco-friendly coloring practices in modern society.

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1. Ali BH, Al-Wabel N, Blunden G. Phytochemical, pharmacological and toxicological aspects of Lawsonia inermis L.: A review. Int J Pharmacol. 2009;5(6):398–406.
2. Mikhaeil BR, Badria FA, Maatooq GT, Amer MMA. Antioxidant and immunomodulatory constituents of Lawsonia inermis. Z Naturforsch C J Biosci. 2004;59(7–8):468–476.
3. Chaudhary G, Goyal S, Poonia P. Lawsonia inermis Linnaeus: A phytopharmacological review. Int J Pharm Sci Drug Res. 2010;2(2):91–98.
4. Singh DK, Luqman S, Mathur AK. Lawsonia inermis L. – A commercially important medicinal plant: A review. Int J Med Arom Plants. 2015;5(1):1–13.
5. Badoni Semwal R, Semwal DK, Combrinck S, Cartwright-Jones C, Viljoen A. Lawsonia inermis L. (Henna): Ethnobotanical, phytochemical and pharmacological aspects. J Ethnopharmacol. 2014;155(1):80–103.
6. Habbal OA, Al-Jabri AA, El-Hag AH, Al-Mahrooqi ZH, Al-Hashmi NA. In vitro antimicrobial activity of Lawsonia inermis Linn (Henna): A pilot study on the Omani henna. Saudi Med J. 2005;26(1):69–72.
7. Gupta P, Birdi TJ. Development of botanicals to combat antibiotic resistance. J Ayurveda Integr Med. 2017;8(4):266–275.
8. Kartal M, Yıldız S, Kaya S, Kurucu S, Topçu G. Antimicrobial activity of Lawsonia inermis extracts and isolated compounds. Phytother Res. 2003;17(8):987–989.
9. Morrison RT, Boyd RN. Organic Chemistry. 7th ed. New Delhi: Pearson Education; 2011.
10. Bahl A, Bahl BS. Advanced Organic Chemistry. New Delhi: S. Chand Publishing; 2019.
11. National Council of Educational Research and Training. Chemistry in Everyday Life: NCERT Textbook for Class XII. New Delhi: NCERT; 2024.
12. Gupta AK, Foley KA. Adverse reactions associated with para-phenylenediamine in hair dyes and temporary tattoos. Dermatitis. 2019;30(2):89–95.

Mehandi (Henna), derived from the plant Lawsonia inermis, is one of the oldest natural dyes used for body art, hair coloring, and traditional medicinal applications. Beyond its cultural significance, henna represents an interesting example of applied organic chemistry, where naturally occurring molecules interact with biological tissues to produce long-lasting coloration. The primary coloring constituent of henna is Lawsone (2-hydroxy-1,4-naphthoquinone), a naphthoquinone compound responsible for the characteristic reddish-brown stain. When henna paste is applied to skin or hair, Lawsone penetrates the outer layers and reacts with amino groups present in keratin proteins through covalent bonding mechanisms, resulting in stable dye-protein complexes. The staining intensity is influenced by factors such as pH, temperature, oxidation, and the presence of terpenes from essential oils. Acidic conditions facilitate dye release, while heat and oxidation enhance color development and permanence. This article discusses the chemical composition of henna, the molecular mechanism of dye formation, and the roles of various paste ingredients in improving staining efficiency. Furthermore, a comparison between natural henna and synthetic black henna containing para-phenylenediamine (PPD) is presented, highlighting the chemical basis of allergic reactions and associated health risks. The review also examines the applications of henna in cosmetics, hair dyes, textile coloration, and medicinal formulations. Through an exploration of its chemistry, henna emerges as a sustainable, environmentally friendly, and biologically compatible alternative to many synthetic dyes. Understanding the molecular interactions involved in henna staining provides valuable insights into natural dye chemistry while emphasizing the importance of safe and eco-friendly coloring practices in modern society.

🔒 This is a subscription article

Full text is available to subscribers and institutional members. Please choose an option below to access it.

1. Ali BH, Al-Wabel N, Blunden G. Phytochemical, pharmacological and toxicological aspects of Lawsonia inermis L.: A review. Int J Pharmacol. 2009;5(6):398–406.
2. Mikhaeil BR, Badria FA, Maatooq GT, Amer MMA. Antioxidant and immunomodulatory constituents of Lawsonia inermis. Z Naturforsch C J Biosci. 2004;59(7–8):468–476.
3. Chaudhary G, Goyal S, Poonia P. Lawsonia inermis Linnaeus: A phytopharmacological review. Int J Pharm Sci Drug Res. 2010;2(2):91–98.
4. Singh DK, Luqman S, Mathur AK. Lawsonia inermis L. – A commercially important medicinal plant: A review. Int J Med Arom Plants. 2015;5(1):1–13.
5. Badoni Semwal R, Semwal DK, Combrinck S, Cartwright-Jones C, Viljoen A. Lawsonia inermis L. (Henna): Ethnobotanical, phytochemical and pharmacological aspects. J Ethnopharmacol. 2014;155(1):80–103.
6. Habbal OA, Al-Jabri AA, El-Hag AH, Al-Mahrooqi ZH, Al-Hashmi NA. In vitro antimicrobial activity of Lawsonia inermis Linn (Henna): A pilot study on the Omani henna. Saudi Med J. 2005;26(1):69–72.
7. Gupta P, Birdi TJ. Development of botanicals to combat antibiotic resistance. J Ayurveda Integr Med. 2017;8(4):266–275.
8. Kartal M, Yıldız S, Kaya S, Kurucu S, Topçu G. Antimicrobial activity of Lawsonia inermis extracts and isolated compounds. Phytother Res. 2003;17(8):987–989.
9. Morrison RT, Boyd RN. Organic Chemistry. 7th ed. New Delhi: Pearson Education; 2011.
10. Bahl A, Bahl BS. Advanced Organic Chemistry. New Delhi: S. Chand Publishing; 2019.
11. National Council of Educational Research and Training. Chemistry in Everyday Life: NCERT Textbook for Class XII. New Delhi: NCERT; 2024.
12. Gupta AK, Foley KA. Adverse reactions associated with para-phenylenediamine in hair dyes and temporary tattoos. Dermatitis. 2019;30(2):89–95.