Henna

Henna (Lawsonia inermis L.)

1. Identity: Botanical Classification, Nomenclature, and Natural Source

Lawsonia inermis Linn, commonly known as henna, is a member of the Lythraceae family and has been found to contain a variety of compounds with both industrial and medicinal applications in its stem, bark, roots, flowers, and seeds. Henna belongs to the genus Lawsonia, which is monotypic — this means it is the only species in its genus. The botanical name Lawsonia was given in commemoration of Dr. Isaac Lawson, an 18th-century Scottish doctor. The species name inermis refers to the usually spineless twigs of the plant, which separate it from other thorny shrubs.

Lawsonia inermis Linn (Family: Lythraceae) is a much-branched glabrous shrub or small tree, 2–6 m in height, cultivated primarily for its leaves, believed to have originated in the Middle East and North Africa, and then spread across Asia thousands of years ago. Today, henna is cultivated around the world, from South America to Japan. It can also be found growing in the wild in Pakistan and India. This small shrub is adapted to a wide range of hot environments, including tropical and subtropical forests, shrublands, grasslands, deserts and wetlands. It can tolerate both acidic and alkali soils as well as heavy and sparse rainfall, allowing it to thrive in many countries.

L. inermis has a large number of vernacular names, which highlight its extensive cultural and medicinal use. It is "henna" or "Egyptian privet" in the English language. It is named as "mehndi" in Urdu and Hindi, "mendi" in Gujarati and Marathi, and "maruthani" in Tamil.

1.1 Common Forms and Preparations

Henna is commercially and traditionally available in a range of forms derived from different parts of the plant:

• Dried leaf powder: Henna is a dye made from dried, powdered leaves of Lawsonia inermis, used to produce reddish stains used in body art. The powder is typically hydrated with water, lemon juice, or tea to form a paste prior to application to skin or hair.
• Essential oil: Henna essential oil (HeEO) is extracted from the leaves and small flowers of L. inermis by hydrodistillation and has applications in perfumery.
• Hydroalcoholic and solvent extracts: Scientific studies have employed a range of extraction solvents. L. inermis leaf extracts have been prepared by macerating in ethanol, methanol, chloroform, hexane, and water boiling.
• Topical pharmaceutical formulations: Research preparations include ointments (e.g., 1% henna ointment) and hydrogels containing standardized hydroalcoholic extracts. One pilot study formulated a standardized topical hydrogel containing the hydroalcoholic extract (10%) of henna and evaluated its clinical efficacy; the topical dosage form was standardized based on its lawsone content.
• Spray-dried extract: Spray drying of an aqueous henna leaf extract using a co-current spray dryer yielded a brown, fine powder with a 33–35% yield.
• "Black henna": A commercially distinct product that is not a pure botanical preparation. Black henna contains the two main constituents of red henna and paraphenylenediamine (PPD), and other ingredients are often added, which are often heavy metals.

2. Traditional and Historical Use

2.1 Ancient Civilizations

The use of Lawsonia inermis L. (henna) for medicinal and cosmetic purposes is inextricably linked to ancient and modern cultures of North Africa and Asia. Literature and artwork indicate that Lawsonia inermis played an important holistic role in the daily lives of some ancient cultures, providing psychological and medicinal benefits, as well as being used for personal adornment.

Henna originates in North Africa and the Middle East, and has been used since at least antiquity across the region, including in ancient Egypt, as well as in ancient Mesopotamia and broader pre-Islamic Arabian cultures, as a hair and body dye, notably in the temporary body art of mehndi (or "henna tattoo") resulting from the staining of the skin using dyes from the henna plant. One of the earliest uses of henna can be dated back to Ancient Egypt, where henna paste was used to stain mummies and mummy wrappings. The Egyptians believed henna retained a person's spirituality. The lawsone also made the skin stronger and resistant to decay.

2.2 Medicinal Traditional Uses

Although henna was historically applied to the hands and feet to protect against fungal pathogens and to hair to combat lice and dandruff, other traditional uses include the treatment of liver and digestive disorders, reduction of tissue loss in leprosy, diabetic foot disorders and ulcers.

The plant has been traditionally used to treat numerous conditions, including ulcers, bronchitis, lumbago, hemicrania, leukoderma, scabies, boils, ophthalmic disorders, hair loss, and jaundice.

According to Persian medicine resources such as Rhazes' Liber Continens (865–925 AD), the Canon of Medicine by Avicenna (980–1037 AD), and the Storehouse of Medicaments written by Aghili Shirazi (1670–1747 AD), henna (Lawsonia inermis L.) is a plant that has anti-inflammatory, antimicrobial and skin-enhancing properties, all of which are beneficial for people who have to use artificial limbs.

The traditions of henna for wellness have not become as fashionable as the body art and hair dye, but there has been increasing investigation by researchers into folk uses of henna as a genuinely pharmacologically active plant rather than merely a cultural artifact.

2.3 Cultural and Ritual Use

Henna has been used to dye the skin, nails, and hair of women and men in many cultures and religions across its area of natural distribution and beyond. Its use has been especially common among women as part of fertility and marriage celebrations. The oil from henna flowers has been used to create perfumes since ancient times. The plant is also a good repellent of insects and mildew and is used to preserve leather and cloth.

In several countries, henna decoction is ingested as a traditional drug to induce abortion. This practice carries serious documented risks (see Safety section).

3. Key Constituents and Active Compounds

3.1 Primary Phytochemical Profile

Lawsonia inermis contains a variety of bioactive compounds, including flavonoids, coumarins, triterpenoids, steroids, xanthones, polyphenols, fatty acids, alkaloids, quinones, tannins, leucocyandin, epicatechin, catechin, and quercetin. Almost 70 phenolic compounds have been isolated from various parts of the plant. Naphthoquinones, which include the dyeing principle lawsone, have been linked to many of the pharmacological activities.

Almost a hundred phytoconstituents, representing a variety of classes, have been identified from all parts of Lawsonia inermis.

3.2 Lawsone (2-Hydroxy-1,4-naphthoquinone): The Principal Bioactive Compound

Lawsone, a naturally occurring organic compound also called hennotannic acid, is obtained mainly from Lawsonia inermis (henna). It is a potential drug-like molecule with unique chemical and biological characteristics. The plant is particularly famous for yielding a reddish-orange colour from the compound lawsone (2-hydroxy-1,4-naphthoquinone), which is found primarily in its leaves. Lawsone is the major active compound that gives henna its colouring properties, which have contributed to its being a standard ingredient in cosmetic and ceremonial applications for centuries.

The colouring agent in henna is related to lawsone (2-hydroxy-1,4-naphthoquinone) which reacts with skin keratin. Its principal pigment, lawsone (2-hydroxy-1,4-naphthoquinone), binds to keratin and forms a stain that can last weeks on hair and several days on skin.

3.3 Other Identified Compounds

The plant is reported to contain lawsone, esculetin, fraxetin, isoplumbagin, scopoletin, betulin, betulinic acid, hennadiol, lupeol, lacoumarin, laxanthone, flavone glycosides, and two pentacyclic triterpenes. Other naphthoquinone derivatives such as lawsoinermone and lawsoniaside (1,2,4-trihydroxynaphthalene-2-O-β-D-glucopyranoside) can also be obtained from leaves of henna. Among compounds identified within the Lawsonia genus are: p-coumaric acid, 2-methoxy-3-methyl-1,4-naphthoquinone, and apiin. Other compounds such as lawsone, apigenin, luteolin, and cosmosiin had previously been identified.

In addition to other volatile terpenes, some non-volatile terpenoids, a single sterol, two alkaloids and two dioxin derivatives have also been isolated from the plant. GC/MS analysis revealed at least 30 different components in henna leaves.

3.4 Established Mechanisms of Action

The pharmacological mechanisms of henna constituents operate across multiple pathways, primarily attributed to lawsone and the phenolic/flavonoid fraction:

• Antioxidant activity: Results have shown that lawsone has potential antioxidant, anti-inflammatory, antimicrobial and antitumor properties. Antioxidant effects are mediated through free radical scavenging and inhibition of lipid peroxidation. Butanolic fractions of L. inermis leaves effectively scavenged hydroxyl radicals and inhibited lipid peroxidation in laboratory assay systems.
• Anti-inflammatory pathway: Isolated compounds from L. inermis showed marked anti-inflammatory, analgesic, and antipyretic activity, lending scientific credence to the use of the plant in traditional systems of healing. With an IC50 value of 510.23 mg/l, it was confirmed that the methanolic extract exhibited the strongest anti-inflammatory action when compared to all other investigated extracts.
• Antimicrobial: Lawsone has potential antioxidant, anti-inflammatory, antimicrobial and antitumor properties. Secondary metabolites, particularly the naphthoquinone lawsone, are thought to disrupt microbial cell membrane integrity.
• Antidiabetic / alpha-glucosidase inhibition: Previous studies uncovered potent inhibitory effects of lawsone (2-hydroxy-1,4-naphthoquinone) against α-glucosidase, which gave insight to compare the hypoglycemic and hypolipidemic effects of lawsone in high-fat/high-fructose-diet- and nicotinamide-streptozotocin-induced diabetic rats.
• Anticancer: Lawsone also induces cell cycle inhibition and programmed cell death in cancer, making it a potential chemotherapeutic agent.
• Hemolytic/oxidative mechanism (adverse): Like other ortho-substituted 1,4-naphthoquinones, lawsone induces oxidative injury to red blood cells, that could be fatal in G6PD-deficient infants and rarely in children and adults.

4. Scientific Evidence by Area of Use

4.1 Antimicrobial Activity

Evidence type: Predominantly in vitro; some animal models. No robust clinical trials.

Although a myriad of pharmacological activities have been documented, the antioxidant and antimicrobial activities are the most thoroughly investigated.

In one study, the antimicrobial activity of Lawsonia inermis was investigated against clinical isolates of seven bacteria including four Gram-negative (Escherichia coli, Salmonella typhi, Klebsiella spp., Shigella sonnei) and three Gram-positive (Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis) using the disc diffusion method. Four types of Lawsonia inermis extracts were prepared using methanol, chloroform, acetone and water as extraction solvents. Lawsonia inermis displayed noteworthy antimicrobial activity against both Gram-positive and Gram-negative bacterial strains used in the study.

Regarding antifungal activity, one study investigated the antifungal effect of chloroform, methanol, and water extracts of henna leaves on Malassezia species using miconazole nitrate as a reference antibiotic. Malassezia species are normal skin flora that cause pityriasis versicolor and folliculitis under suitable conditions. The reported results showed that the chloroformic and methanolic henna extracts inhibit the growth of Malassezia species at different concentrations; however, the water extract was the most active as compared with the miconazole nitrate standard antibiotic.

When combined with plant extract, the antifungal nystatin displayed increased action, suggesting potential for synergistic combination approaches.

A 2025 PeerJ study provided updated in vitro evidence: Gallic acid, catechin, ellagic acid, apigetrin, lawsone and quercetin were identified by HPLC. Ethanol and methanol extracts exhibited strong antioxidant properties, and the extracts showed different inhibition of bacterial growth, especially against B. cereus and S. aureus. In addition, all extracts had potential inhibitory activity against all fungal strains tested, especially the ethanol and methanol extracts, which exhibited strong antifungal activity against Penicillium sp.

Evidence limitations: Nearly all antimicrobial studies to date are in vitro or use animal models. The clinical relevance of laboratory minimum inhibitory concentrations (MICs) for topical human use remains to be established through appropriately designed trials.

4.2 Wound Healing

Evidence type: Animal studies; limited human pilot trials.

One animal study assessed the wound healing potential and antimicrobial activity of henna, pomegranate, and myrrh extract formulations and their blend in excision and dead space wound models in rats in comparison to a marketed ointment (gentamicin).

A pilot human clinical trial (PMC, 2022) specifically assessed henna for wound healing in patients with recessive dystrophic epidermolysis bullosa (RDEB), a rare hereditary skin fragility disorder. The aim was to evaluate a topical formulation of henna (Lawsonia inermis Linnaeus) in the management of wounds and the itching sensation in patients with EB. This was a pilot single-arm clinical trial. Nine patients with recessive dystrophic EB, with an age range of 5 to 32 years, were enrolled. The patients were instructed to apply the topical 1% henna ointment once daily on two erosions and on two sites with moderate to severe itching. The total duration of the intervention was 4 weeks with weekly follow-up visits. There was a significant improvement in the skin symptoms of epidermolysis bullosa including skin redness, itching, burning, and local warmness (P < 0.05). The present study showed that 1% henna ointment had an acceptable effect on skin characteristics in patients with EB. In fact, all the selected wounds of these patients were clinically improved during the first two weeks of the study.

In another randomized clinical trial examining contact dermatitis in prosthetic limb users: The aim was to assess the efficacy of a topical henna preparation in the management of contact dermatitis in patients using lower limb prosthetics. The randomized, double-blind, placebo-controlled clinical trial was conducted on 95 participants with lower extremity amputation using limb prosthetics, aged 12–70 years who complained of contact dermatitis. They were randomly assigned to receive either two weeks of topical henna preparation every night as the intervention group, or topical placebo as the control group.

Evidence limitations: The wound-healing EB pilot study enrolled only nine patients and was uncontrolled (single-arm). The evidence for wound healing remains preliminary and is insufficient to support general therapeutic claims without further adequately powered, controlled trials.

4.3 Anti-inflammatory and Analgesic Effects

Evidence type: In vitro and animal studies; limited human data as secondary endpoints.

Different parts of henna have been shown to have biological, pharmacological, and chemical activities, including antibacterial, antifungal, antitumor and antiproliferative, antiangiogenic, larvicidal, antileishmanial, lousicide, antimalarial, hepatoprotective, wound healing, anti-inflammatory, analgesic, antipyretic, memory enhancement, enzyme inhibitor, and antioxidant activities.

One study aimed to estimate the anti-inflammatory property and antibacterial effects of Lactiplantibacillus plantarum and ethanol extracts of Lawsonia inermis leaves against Staphylococcus aureus when used separately or collectively as a synergism. An experimentally induced infected wound model in mice was created and divided into 10 groups then treated for two days. The antibacterial, anti-inflammatory, and wound healing activity were evaluated through histopathological sections taken before and after treatment.

Evidence limitations: Anti-inflammatory and analgesic data for L. inermis in humans are almost entirely absent as primary clinical trial endpoints. Effects demonstrated in animal models or in vitro should not be extrapolated directly to clinical efficacy.

4.4 Palmar-Plantar Erythrodysesthesia (Hand-Foot Syndrome) in Oncology

Evidence type: Randomized controlled feasibility trial (56 participants); pilot RCT (18 participants).

This is among the most clinically specific areas where human trial data exist for henna. Palmar-plantar erythrodysesthesia (PPE), also referred to as hand-foot syndrome, is a common dermatologic toxic reaction that occurs with capecitabine and pegylated liposomal doxorubicin (PLD), either as monotherapy or in combination. PPE is manifested clinically as painful erythema, preceded by paresthesia, of palms and soles during treatment with anticancer drugs.

One study was a randomized controlled feasibility study in three specialized tertiary cancer centers with 56 patients with a PPE grade 1 or above and various cancer diagnoses. The intervention included the local application of henna to the affected areas. The control group followed the same process with an inert henna substitute. A statistically significant interaction was found between Group and Time over the weekly measurements of HFS-14 scores (F=5.009, p<0.002), indicating the significant effect of the intervention throughout the weekly assessments. The trial provided preliminary evidence on henna's effectiveness for treating PPE during treatment with capecitabine or PLD, with lower PPE grades, better performance status and better health-related quality of life observed in the henna group.

A second pilot randomized double-blind placebo-controlled clinical trial examined topical L. inermis L. hydrogel in fluorouracil-induced hand-foot syndrome. Hand-foot syndrome is a frequent dose-limiting adverse reaction of fluoropyrimidine drugs like capecitabine and 5-fluorouracil in breast and gastrointestinal cancers. It has been shown that conventional application of Lawsonia inermis L. (henna) is effective in ameliorating the skin lesions. In this study the researchers formulated a standardized topical hydrogel containing the hydroalcoholic extract (10%) of henna and evaluated its clinical efficacy for the management of fluorouracil-associated HFS.

Evidence limitations: The primary RCT was explicitly a feasibility trial with only 56 participants — not powered to serve as definitive evidence. The hydrogel pilot trial enrolled only 18 patients. Both trials require replication in larger, adequately powered confirmatory studies.

4.5 Antidiabetic / Hypoglycemic Effects

Evidence type: In vitro and animal models only; no human clinical trials identified.

Previous studies uncovered potent inhibitory effects of lawsone (2-hydroxy-1,4-naphthoquinone) against α-glucosidase. Comparison of the hypoglycemic and hypolipidemic effects of lawsone methyl ether (LME) and lawsone was made in high-fat/high-fructose-diet- and nicotinamide-streptozotocin-induced diabetic rats for 28 days. LME and lawsone at the doses of 15, 30, and 45 mg/kg, respectively, produced a substantial and dose-dependent reduction in the levels of fasting blood glucose (FBG), HbA1c, and food/water intake while boosting the insulin levels and body weights of diabetic rats.

Additionally, the levels of total cholesterol, triglycerides, HDLs, LDLs, AST, ALT, creatinine, and BUN in diabetic rats were significantly normalized by LME and lawsone, without affecting normal rats. LME at a dose of 45 mg/kg exhibited the most potent antihyperglycemic and antihyperlipidemic effects, which were significantly comparable to glibenclamide but higher than those of lawsone alone.

The ethanolic extracts of Lawsonia inermis leaves were tested in vitro for alpha-glucosidase inhibitory activity. No human clinical trials on the antidiabetic activity of henna have been identified in the peer-reviewed literature. All hypoglycemic evidence remains preclinical.

4.6 Anticancer / Antitumor Activity

Evidence type: In vitro cell line studies and animal models only. No human clinical trials.

Lawsonia inermis has been shown to induce apoptosis in various cancer cell lines and exhibit antioxidant properties. All extracts showed cytotoxic effects in the cell lines MDA-MB-231, SW480, A549 and A549RT-eto. The ethanol and methanol extracts exhibited the best IC50 values of 57.33 ± 5.56 µg/ml and 65.00 ± 7.07 µg/ml against SW480 cells, respectively.

In an in vivo two-stage mouse skin carcinogenesis study using UV-B radiation for initiation and TPA for tumor promotion, oral administration of henna (0.0025%) in drinking water or oral intake of lawsone (0.0025%) reduced tumor incidence by 66% and 72% respectively, in 10 weeks of treatment. Likewise, same results were obtained when henna (0.5 mg/mL) or lawsone (0.015 mg/mL) were applied topically on the dorsal skin in UV-B-irradiated animals. The authors recommended the addition of henna powder or lawsone in sunscreen agents to acquire a complementary anticancer potential against UV-induced skin carcinogenesis.

One investigation examined the anticancer activity of henna seed extracts in hexane, chloroform, and methanol against the colon cancer cell line HTC-116. Another experimental study examined the possible anticancer effects of an ethanol extract of the root of L. inermis against mice with Dalton's lymphoma ascites (DLA). The ethanolic root extract reportedly decreased the RBC count, hemoglobin content, and monocytes while reversing the rise in WBC, platelets, and lymphocytes. L. inermis root extract adversely impacted the pathophysiological marker enzyme, lipid profile, and antioxidant activity.

Evidence limitations: All anticancer data are from cell-line experiments or animal tumor models. There are no human trials. In vitro cytotoxicity does not predict clinical efficacy or safety in humans.

4.7 Hepatoprotective Activity

Evidence type: In vitro and animal studies only.

Lawsonia inermis is an ethnomedicinal plant, traditionally known for curing several ailments such as skin diseases, bacterial infections, jaundice, renal lithiases and inflammation. Assessment of in vitro antioxidant and in vivo hepatoprotective potential of the butanolic fraction (But-LI) of L. inermis L. leaves was conducted. In vivo protective potential of But-LI was assessed at 3 doses (100, 200 and 400 mg/kg body weight) against 2-acetylaminofluorene (2-AAF)-induced hepatic damage in male Wistar rats. But-LI effectively scavenged hydroxyl radicals. The fraction also inhibited lipid peroxidation and demonstrated appreciable reducing potential. Treatment of animals with 2-AAF resulted in increased hepatic parameters such as SGOT (2.22 fold), SGPT (1.72 fold), ALP (5.68 fold) and lipid peroxidation (2.94 fold).

In order to protect rat liver from carbon tetrachloride (CCl4)-induced oxidative stress, one study investigated the antioxidant and hepatoprotective characteristics of several fractions derived from the fruits of L. inermis. Numerous L. inermis fruit fractions had significant antioxidant activity.

Evidence limitations: No human clinical trials have investigated hepatoprotective effects of henna. All evidence is preclinical.

4.8 Hair and Scalp Effects

Evidence type: Traditional observation supported by limited laboratory and mechanistic studies.

Henna is traditionally applied to fingertips, fingernails and toenails, where it can reverse damage caused by fingernail fungus through weekly applications. Women's use of henna on their hair protects against UV rays that dry and damage hair, and rids the scalp of lice, ringworm, and dandruff.

It has been reported that the dye generated from L. inermis has an effect on hair growth. However, the published evidence supporting clinical hair-growth promotion is weak, and the traditional uses of henna on scalp disorders (lice, dandruff, ringworm) are supported mainly by reported in vitro antimicrobial and antifungal activity, rather than by controlled human trials.

5. Body Systems and Health Areas

The pharmacological activities documented for Lawsonia inermis span antimicrobial, antioxidant, anti-inflammatory and analgesic, effects on hair, antiparasitic, gastroprotective, hepatoprotective, antitumor, wound and burn healing, and hypoglycaemic activities.

• Integumentary system (skin, nails, hair): Application for body art, hair dyeing, wound care, contact dermatitis, hand-foot syndrome, nail fungus, scalp lice, and dandruff.
• Gastrointestinal system: Traditional use for ulcers, digestive disorders, and gastroprotective activity documented in animal models.
• Hepatic system: Traditional treatment of jaundice; hepatoprotective activity in animal models.
• Endocrine/metabolic system: Preclinical evidence for hypoglycemic and hypolipidemic effects via α-glucosidase inhibition.
• Immune and oncology: In vitro induction of apoptosis in cancer cell lines; antiparasitic and immunomodulatory activity documented in laboratory models.
• Hematologic system (adverse interaction): Documented risk of oxidative hemolysis in individuals with G6PD deficiency.

6. Dosage Forms and Reported Dosages

The following dosages are reported directly from cited scientific sources and should not be interpreted as clinical recommendations:

• Topical ointment (clinical pilot, epidermolysis bullosa): Patients were instructed to apply the topical 1% henna ointment once daily on two erosions and on two sites with moderate to severe itching.
• Topical hydrogel (pilot RCT, hand-foot syndrome): A standardized topical hydrogel containing the hydroalcoholic extract (10%) of henna was formulated and evaluated; the topical dosage form was standardized based on its lawsone content.
• Oral lawsone in rodent diabetic model: Lawsone was administered at doses of 15, 30, and 45 mg/kg in diabetic rats for 28 days, producing a dose-dependent reduction in fasting blood glucose, HbA1c, and food/water intake.
• In vivo mouse anticancer model: Oral administration of henna at 0.0025% in drinking water, or topical application of henna (0.5 mg/mL) or lawsone (0.015 mg/mL) on dorsal skin, was studied in UV-B-irradiated mouse models over 10 weeks.
• Hepatoprotective animal study: In vivo protective potential of L. inermis butanolic fraction was assessed at 3 doses — 100, 200 and 400 mg/kg body weight — against experimentally induced hepatic damage in male Wistar rats.
• Body art / cosmetic use (traditional and observational): After henna stains reach their peak colour, they hold for a few days and then gradually wear off by way of exfoliation, typically within one to three weeks.

No standard therapeutic dosage has been established through clinical pharmacokinetic studies for internal use in humans. The clinical trials that do exist have used topically applied preparations.

7. Safety Considerations and Known Interactions

7.1 G6PD Deficiency: Hemolytic Risk

The most clinically significant safety concern associated with natural henna is its potential to induce hemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, a condition with high prevalence in some henna-using populations.

Henna usually carries no significant medical complications in a healthy individual. However, henna in a patient with G6PD deficiency can cause serious medical complications, including severe hyperbilirubinemia and hemolytic anemia, due to its oxidative stress on the erythrocyte.

A literature review summarized the clinical and laboratory findings of 31 G6PD-deficient pediatric patients with henna-induced hemolytic anemia (HIHA). The reported adverse effects of HIHA included death (N: 2), kernicterus (N: 3), life-threatening hemolytic anemia that required blood transfusion (N: 9), and severe hyperbilirubinemia requiring exchange transfusion (N: 7).

Over a 10-year period, 15 G6PD-deficient male newborns were admitted to Al-Jahra Hospital with acute haemolysis a few days after applying henna dye over the body, which is a unique Bedouin tribal practice to celebrate the arrival of the first-born boy. Laboratory investigations revealed significant anaemia, reticulocytosis and indirect hyperbilirubinaemia among the index newborns as compared with controls (p < 0.001). The mean haemoglobin concentration in index patients was 113.4 g/l vs 171.2 g/l in controls.

Henna can cause hemolysis in G6PD-deficient patients because of lawsone (2-hydroxy-1,4-naphthoquinone) which has oxidative properties similar to naphthalene. Percutaneous henna absorption is well recognized and clinical findings support the harmful effect of henna on G6PD-deficient red blood cells.

In several countries, henna decoction is ingested as a traditional drug to induce abortion. Lawsone can induce hemolysis in G6PD-deficient patients after cutaneous exposure or ingestion.

7.2 "Black Henna" and Paraphenylenediamine (PPD) Toxicity

Paraphenylenediamine (PPD) is an oxidative chemical allergen that can cause hypersensitivity reactions. PPD intoxication could cause severe systemic adverse effects like acute renal failure, rhabdomyolysis and multiple organ failure.

A reported case involved a 9-year-old female patient who developed multiple organ failure and cardiac arrhythmia as a result of extensive application of PPD added to henna to the skin. Plasma exchange and continuous venovenous hemodiafiltration were initiated. The patient died on day 4 after developing ventricular fibrillation that was resistant to antiarrhythmic treatment and defibrillation.

Apart from the lawsone molecule, which can cause severe to moderate changes in G6PD-deficient patients, it can cause allergic contact reactions even in patients without a history of G6PD deficiency. Black henna contains the two main constituents of red henna and PPD, and other ingredients added to this product are often heavy metals.

7.3 Adulteration and Quality Control

Adulteration of henna is very common and may have resulted in unwarranted scientific findings. Phytochemical profiling studies of the plant, which are crucial for the establishment of proper quality control protocols, are lacking and hamper the development of medicinal products. Although many in vitro studies have been conducted to evaluate the pharmacological activities and many in vivo studies have focused on the toxicity of extracts, more in vivo studies to validate pharmacological activities are needed. The roles of specific compounds and their synergies have not been comprehensively investigated.

7.4 Allergic Contact Dermatitis

This natural hair dye does not cause significant adverse effects on the body in most people. After using henna, there have been reports of mild contact allergic reactions and hemolytic anemia (more severe cases) in people with G6PD deficiency. Allergic contact dermatitis to pure henna (without PPD) has also been documented in the literature, though it is less common than reactions associated with adulterated products.

7.5 Exclusion Criteria Observed in Clinical Trials

Exclusion criteria observed in published clinical trials included a positive history of allergic reaction to henna, or glucose-6-phosphate dehydrogenase (G6PD) deficiency, and any other systemic diseases.

7.6 Evidence Gaps and Overall Evidence Assessment

Despite extensive traditional use and emerging pharmacological validation, challenges remain regarding extract standardisation, clinical evaluation, and mechanistic understanding. Advanced studies, including clinical trials and bioavailability optimisation, are needed. Hurdles like extract standardisation, toxicity testing, and strict clinical trials are still present.

It has been found to possess a range of pharmacological activities, including antioxidant, anti-inflammatory, analgesic, antiparasitic, hepatoprotective, antifungal, antitumor, wound healing, and hypoglycemic effects. The potential of Lawsonia inermis for various biological applications is promising, and further studies are needed to fully explore its therapeutic benefits for various diseases of public health.

References

• Therapeutic potential of Lawsonia inermis Linn: a comprehensive overview — PMC / Naunyn-Schmiedeberg's Archives of Pharmacology (2024)
• Lawsonia inermis L. (henna): ethnobotanical, phytochemical and pharmacological aspects — Journal of Ethnopharmacology, PubMed (2014)
• Lawsone Unleashed: A Comprehensive Review on Chemistry, Biosynthesis, and Therapeutic Potentials — PMC (2024)
• Unveiling the potentials of Lawsonia inermis L.: its antioxidant, antimicrobial, and anticancer potentials — PeerJ / PMC (2025)
• Lawsonia inermis L. (Henna): A Comprehensive Review of Its Phytochemistry, Pharmacological Potential, Traditional Uses, and Commercial Applications — Journal of Plant Biota (2025)
• Phytochemical, toxicological and antimicrobial evaluation of Lawsonia inermis extracts against clinical isolates of pathogenic bacteria — PMC / Annals of Clinical Microbiology and Antimicrobials (2013)
• Efficacy of a Topical Formulation of Henna (Lawsonia inermis Linnaeus) on the Itch and Wound Healing in Patients With Epidermolysis Bullosa: a Pilot Single-arm Clinical Trial — PMC (2022)
• Efficacy of a topical formulation of henna (Lawsonia inermis L.) in contact dermatitis in patients using prosthesis: A double-blind randomized placebo-controlled clinical trial — PubMed (2020)
• A randomised controlled feasibility trial to evaluate Lawsonia inermis (henna)'s effect on palmar-plantar erythrodysesthesia induced by capecitabine or pegylated liposomal doxorubicin — European Journal of Oncology Nursing (2021)
• Severe Hyperbilirubinemia Secondary to Henna Application in a Neonate With G6PD Deficiency: A Case Report and Literature Review — PMC (2023)
• Henna (Lawsonia inermis Linn.) inducing haemolysis among G6PD-deficient newborns. A new clinical observation — PubMed (1996)
• Fatal paraphenylenediamine poisoning due to black henna — PubMed (2017)
• Comparative Antihyperglycemic and Antihyperlipidemic Effects of Lawsone Methyl Ether and Lawsone in Nicotinamide-Streptozotocin-Induced Diabetic Rats — PMC (2023)
• Antioxidant and hepatoprotective potential of Lawsonia inermis L. leaves against 2-acetylaminofluorene induced hepatic damage in male Wistar rats — PMC (2017)
• Hemolytic anemia after voluntary ingestion of henna decoction by a young girl with G6PD deficiency — PubMed (2011)
• Lawsonia inermis — an overview — ScienceDirect Topics
• The henna plant: Transcending time, religion and culture — Natural History Museum (NHM London)
• Synergistic Antimicrobial Effect of Lactiplantibacillus plantarum and Lawsonia inermis Against Staphylococcus aureus — PMC (2022)
• Paraphenylenediamine Toxicity — StatPearls, NCBI Bookshelf
• Phytochemical and Pharmacological Activities of Natural Dye Plant, Lawsonia inermis L. (Henna) — Journal of Young Pharmacists (2023)