Henna (Mehndi): The Ayurvedic Herb for Hair and Scalp Care
Plant-based colour, a coating effect on the hair shaft, a cooling sensation on the scalp: henna (Lawsonia inermis) holds a special place in the Ayurvedic tradition. Here is what tradition says, what the scientific data actually show, and — above all — how to use it safely.
Henna in the Ayurvedic Tradition
Henna, or Lawsonia inermis, is a shrub native to the hot regions of Asia and North Africa. In India, its dried and powdered leaves have been used for centuries both for the art of mehndi (temporary skin designs applied for weddings and festivals) and for hair care. In Ayurvedic texts, the plant is known as madayantika and described as cooling, traditionally used to soothe the pitta dosha, which is associated with heat. If these concepts are new to you, our guide what is Ayurveda covers the basics of this traditional system of medicine. One thing should be clear from the outset: these are traditional uses, not proof of efficacy in the medical sense.
Hair and Scalp: What Tradition Reports
In traditional Indian practice, henna is first and foremost a versatile hair treatment:
- Plant-based colour: lawsone, the natural pigment in the leaves, binds to keratin and produces copper to auburn tones depending on your starting shade;
- Coating effect: the pigment deposit wraps around the hair shaft, which can make hair feel thicker and look shinier;
- Cooling sensation: the paste applied to the scalp is traditionally used in hot weather for its refreshing effect;
- Scalp care: tradition credits henna with a cleansing, balancing role, particularly for oily scalps or dandruff.
Henna is often combined with other hair-care herbs from the Indian pharmacopoeia, such as bhringaraj, amla or hibiscus.
What Does the Science Say?
The chemistry of henna is well documented: lawsone (2-hydroxy-1,4-naphthoquinone) binds to the keratin of the hair, which explains both the long-lasting colour and the perceived "coating" effect. On the pharmacological side, a 2014 review by Semwal and colleagues in the Journal of Ethnopharmacology summarises the ethnobotanical uses and laboratory research on Lawsonia inermis, including antimicrobial and antifungal properties observed in vitro (see on Google Scholar). These findings remain preliminary: they do not demonstrate any proven clinical benefit in humans — for hair loss or dandruff, for example. For guidance on how to interpret this kind of evidence, see our article on Ayurveda and science.
How to Prepare and Apply Henna (Hair Use)
- Choose the powder: 100% Lawsonia inermis with no other listed ingredient, khaki-green in colour, with a grassy, hay-like smell;
- Prepare the paste: mix the powder with warm water to a thick, yoghurt-like texture, then let it rest for a few hours so the pigment can release;
- Test first: on a hidden strand of hair (to check the colour result) and on a small patch of skin 48 hours beforehand (to check tolerance);
- Apply: on clean hair, section by section, wearing gloves, then cover with cling film or a shower cap;
- Processing time: from 30 minutes (subtle tones) to 2–3 hours (deeper colour), then rinse thoroughly without shampoo.
The colour oxidises and deepens over the following 48 hours. Because henna is extremely persistent, it is not recommended on chemically coloured hair or before salon bleaching: talk to your hairdresser first.
Pure Henna vs "Black Henna": Beware of PPD
The main risk associated with henna does not come from the plant itself but from adulterated mixtures. The "black henna" used for some temporary tattoos often contains paraphenylenediamine (PPD), a chemical dye that can trigger severe contact dermatitis and lifelong sensitisation, as documented in numerous published dermatology case reports (literature on Google Scholar).
| Criterion | Pure henna | Suspect product |
|---|---|---|
| Powder colour | Khaki green, hay-like smell | Dark brown, black, or an artificial green |
| Promised result | Copper to auburn, never black | "Jet black", "quick brown" |
| Processing time | 1 to 3 hours | Just a few minutes |
| Label | 100% Lawsonia inermis | PPD, metallic salts, picramate, vague wording |
A henna that promises black hair or a result in minutes is not pure henna: do not use it.
Natural Henna vs "Neutral Henna": Don't Confuse Them
The "neutral henna" sold in health-food stores is not henna at all: it is generally Cassia obovata, a plant that adds little or no colour and is used as a conditioning, coating treatment. "Egyptian henna", "Rajasthani henna" or "Yemeni henna", on the other hand, are genuine hennas whose lawsone content varies with origin. Always read the full INCI ingredient list before buying, whether you shop online or in store.
Precautions
- Allergies: always perform a skin patch test 48 hours before any application; strictly avoid PPD-based "black henna", on skin and hair alike;
- G6PD deficiency: henna is not recommended for people with this enzyme deficiency, nor for babies and young children;
- Pregnancy and breastfeeding: as a precaution, ask a healthcare professional before any use, and refuse any product whose composition is unclear;
- Damaged scalp: do not apply henna to irritated or broken skin, or to any undiagnosed skin condition;
- External use only: henna should never be taken orally as self-medication.
If you experience redness, itching or swelling after application, rinse immediately and see a doctor. Henna is a traditional cosmetic treatment, not a therapy: no persistent scalp problem (hair loss, heavy dandruff, itching) should be managed without medical advice. To go further, read our guide on safety and precautions in Ayurveda.
Your questions about henna (mehndi)
Does henna make hair grow faster?
No robust clinical study shows that henna speeds up hair growth. The Ayurvedic tradition regards it as a scalp treatment, and its coating effect can create an impression of extra volume. If you are experiencing persistent hair loss, consult a doctor or dermatologist.
Does henna damage hair?
Pure, good-quality henna does not damage the hair shaft: it coats it. It can, however, be drying on very dry hair, and it makes subsequent chemical colouring unpredictable. Adulterated hennas containing metallic salts or PPD, on the other hand, can cause real damage.
How can I recognise pure henna?
Pure henna lists a single ingredient — Lawsonia inermis — comes as a khaki-green powder with a hay-like smell, and never promises a black result or a few minutes' processing time. Choose brands that are transparent about origin and composition.
What is "black henna" and why is it dangerous?
"Black henna" is a mixture laced with paraphenylenediamine (PPD), a chemical dye that can trigger severe allergic reactions and permanent sensitisation. Many cases of contact dermatitis have been documented in the dermatology literature. It should be avoided on skin and hair alike.
Can I use henna during pregnancy?
Pure henna applied externally has a long history of traditional use, but safety data remain limited and adulterated products pose a real risk. As a precaution, ask a healthcare professional first and only use products with a verified composition.
Does henna suit all hair types?
Henna works best on dark to medium-brown hair seeking copper to auburn tones; on blonde or grey hair, the result can be very orange. It is not recommended on bleached or chemically coloured hair, as the interactions are unpredictable. Always do a strand test first.
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