The Science of Henna and Hair

What is Henna?

Henna, Lawsonia inermis  leaves may be used fresh, though they are more often harvested, dried, and powdered.  When pulverized henna leaves, fresh or dried, are mixed with a mildly acidic fruit juice, the lawsone molecules in the henna will be made available for dyeing.  If you put henna paste on skin or hair, the lawsone molecules will migrate from the plant pulp, into keratin, leaving a red-orange stain. This action is similar to putting a wet teabag on a white tablecloth.  The longer you leave the wet teabag on the tablecloth, the darker the stain.  The longer you leave the henna paste on skin or hair, the more lawsone molecules will have the opportunity to migrate into the keratin,though six hours generally is enough for maximum absorption of henna.  As more lawsone molecules migrate into keratin, the more saturated and rich the color.

Click on the image, and the links above and below to learn more about henna.

Exactly how does henna 'work'? The Chemistry of Henna.
Other brands

There is a wide variety of products available for coloring hair which claim to be pure henna, or which claim to contain pure henna powder along with additional natural plant ingredients. There is no international standard for what can be marketed as henna, and it is often difficult to tell which products are what they claim to be. Many henna for hair products lack an ingredient declaration. A package may show only some ingredients or have no ingredients list at all.

The Botany of Henna

Where and how do you grow henna? Can you grow henna in your garden?

Henna is Lawsonia inermis Fam. Lythraceae, a monotypic genus, the single example being L. inermis,2 native to North and East Africa, introduced and cultivated in the Persian Gulf region, the Arabian Peninsula, the Levant, and South Asia.3 It grows in semi-arid tropical zones, in dry sandy, iron-rich soils, and is adapted to extended drought. It does not tolerate frost and thrives where temperatures are between 11C and 45C.  Henna is a biennial dicotyledonous, herbaceous, shrub-like desert tree. It will naturally grow six to twenty feet in height; under cultivation the tree is pruned once or twice a year to a short bush to produce more henna leaves per hectare.

The Phytochemistry of Henna

Page 17: The Phytochemistry of Henna

Other than lawsone, what occurs naturally in henna? The naphthoquinones in henna have received the greatest research attention, as the dye properties, antimicrobial, and strong antioxidant effects proceed from these.  Henna contains a number of naphthoquinones including 2-methoxy-3-methyl- 1,4-naphthoquinone and lawsone (2-hydroxy-1,4-naphthoquinone). These henna naphthoquinones are derived from naphthalenes. A small number of naphthalenes, lawsoniaside (1,2,4-trihydroxynaphthalene-1,4-di-β-D-glucopyranoside) 1,2,4-trihydroxynaphthalene-1-O-β-D-glucopyranoside three methyl naphthalene carboxylates, lawsonaphthoate A-C, and 1,2-dihydroxy-4-Oglucosyloxynaphthalenehave been isolated from henna stems and leaves.
henna leaf
Henna products in the marketplace frequently contain unlisted additives and adulterants, and the millingand sifting varies with particles from 0.2 mm to over 3 mm.  Consumers become frustrated by henna products’ coarse sift, sand, problematic interactions with chemical dyes, and unpredictable, fading results. The public understanding of what is henna is further misinformed by false advertising claims made by by exporters and retailers.

Ancient SunriseŽ Chapter 5: Plants that Dye Hair

Page 5: Henna, Lawsonia Inermis

compound henna
Ancient SunriseŽ Chapter 3: Compound Henna

Go to these pages these to learn about the addition of metallic salts and oxidative dyes to henna, how these created conflicts with chemical hair dye, and well as confusion about what henna actually is.

How did dye formulators first change henna colors to brown and black with metallic salts?

Index of specific topic in this chapter:

Pag 3: Compound henna, rasticks, henna-reng, henna-rasticks, and metallic salts

Page 33: Henna mislabeling, misinformation and disinformation

Page 50: Para-phenylenediamine and henna

Page 87: Walnut, Silver Nitrate, and Para-phenylenediamine as Brunette Hair Dye
Ancient SunriseŽ Chapter 5: Plants that Dye Hair

This chapter discusses henna, indigo, and cassia, (lawsonia inermis, indigofera tinctoria, and cassia obovata) and the chemistry of each of these dye plants. Understanding the botany of these plants will help you understand how to get the best results from your henna hair dye.

  Index of specific topics in this chapter:

Page 3: Three Plants Dye Hair: Henna, Indigo, and Cassia

These three plants all can be used to dye hair, but they have different characteristics, so is you try to just put the different powders in a mix and add hot water, you will get inferior results that fade quickly and go brassy.

Page 5: Henna, Lawsonia Inermis

What is a Michal Addition and acidic hydrolysis and why are they crucial to getting the best results from  your henna?  How do you make these happen?

Page 15: Indigo, Indigofera Tinctoria

What is indigo, and why do you have to mix it separately and differently from henna?

Page 21: Cassia Obovata

What is cassia, how do you mix it, and what will it do for YOUR hair?

Ancient SunriseŽ Chapter 6 : Henna and Acidic Mixes

These pages discusses the necessary chemistry of mixing henna and cassia with a mildly acidic liquid.  This chapter discusses several sources of fruit acids, and how each has a different effect on henna.

Index of specific topics in this chapter:

Page 3: Henna, Cassia, and Mildly Acidic Mixes

Page 5: Citrus Fruits and Citric Acid

Page 7: Ancient SunriseŽ Amla, Emblica Officinalis

Page 8: Acids with Anthocyanins and Antioxidants

Page 11: Ancient SunriseŽ Kristalovino and Ancient SunriseŽ Malluma Kristalovino

Page 13: What Acids Do You Have Around the House?

Page 14: Coffee, Wine, Yogurt, Oil and Eggs: Don’t Bother (totally useless)

How do manufacturers
of "henna hair dye" make all those different henna colors? Boxes of commercially produced “henna for hair” come in a range of colors. Henna, itself, DOES NOT come in a range of colors.  

The only dye molecule in henna (Lawsonia Inermis) in sufficient quantity to stain hair is Lawsone , which is a red-orange molecule.  Any company that claims they create the wide range of henna colors with 100% henna,  using roots, bark, or other parts of the henna plant to achieve their colors is …… lying or seriously ignorant. Only henna leaves are useful for dying hair, and other parts of the henna plant do not dye hair other colors.  Chemicals, metallic salts or other plants must be added to henna to make any color other than red. 

These pre-mixed colors  are compound hennas.   If you buy a box labeled henna that claims to dye hair blonde, brown or black, there is something other than henna in that box.

Compound Henna Dye: This is a term that refers to hair dye marketed as henna,  and is formulated in different colors. These mixtures may contain additional plant dyes, may contain  metallic salts, and may contain para-phenylenedmine. 

Compond henna may damage your hair.  

Pure body art quality henna is good for your hair.

There is no such plant as "blonde henna", "brown henna" or "black henna". The plant, henna, lawsonia inermis, has only one dye molecule, and that molecule is red-orange.  Chemicals, metallic salts or other dye plants must be added to henna to make any color other than red.  These mixes are termed compound hennas.  Some dye plants can be added to alter the color of henna.  Some chemicals can be added to alter the color of henna.
Metallic salts alter and fix a dye stain. Many “henna colors” are created with metallic salts.  The most frequently used material is lead acetate, though silver nitrate, copper, nickel, cobalt, bismuth and iron salts have also been used.

Dyes with lead acetate gradually deposit a mixture of lead sulfide and lead oxide on the hair shaft.  

When you hear that henna has “metal”, “lead”, or “coats the hair” and “leaves it brittle”, that refers to a compound henna dye, full of these metallic salts. 

Hair bleach, permanent hair color, and permanent wave solution are a disastrous combination with compound (metallic salt) henna dyes. These can result in green, purple, or totally fried hair. 

Some pre-mixed hennas have para-phenylenediamine.  Some pre-mixed hennas have very little henna whatsoever. 

Body art quality henna does NOT have metals, lead, nor does it “coat the hair”.  This website is dedicated to providing you with the information to learn to dye your hair with 100% pure henna, indigo, cassia and amla without using pre-mixed "compound henna".  This is very much like learning to do your own cooking instead of eating processed food.  You'll know what you're getting and you'll know what its doing.  The pre-mixed "compound henna" products may not have an accurate or complete ingredient declaration.   If you cannot be certain what is in each box, you cannot be certain what cross reactions may occur between your compound henna and preceeding or subsequent chemical process, and you won't know if you're going to have an allergic reaction to something in that mixture.   

How can you find out if the henna hair dye you've been using has toxic metallic salts? 

Harvest some of your hair. 

Mix one ounce (30 ml) of 20-volume peroxide and 20 drops of 28% ammonia. 
Put your harvested hair in the peroxide-ammonia mix (this is in synthetic hair dye).

If there's lead in the henna you've used, your hair will change color immediately.

If there's silver nitrate in the henna you've been using, there will be no change in hair color, because silver is coating the hair. However, silver nitrate leaves a greenish cast to your hair, so you can tell by that. 

If there's copper in the henna you've used, your hair will start to boil, the hair will be hot and smell horrible, and the hair will disintegrate.

With all that crap, frequently unlisted, in some henna products, no wonder henna's gotten a bad rap!

Why do some boxes of "colored henna" have no declaration of ingredients?

Some countries where these products are initially manufactured do not have laws requiring the declaration of ingredients in cosmetics. So, they can put anything they want in that box and they don't have to tell you what's in it.  If someone in the USA imports these mixes, they are not required by law to go back and discover what's in the bulk mix that was passed through customs marked as "henna", and they don't have to declare it on their package.  This is how a company can have a dozen "colors of henna" from blonde to black, and sell them without listing their ingredients .. and they usually do. The person selling the product may have no idea what's in the box, or they may know and not want to tell you.   If its a box of hair dye that claims to be henna and it claims to dye hair something other than red, and the powder inside is not green ... it is NOT HENNA.  Many products labeled "herbal henna" actually contain para-phenylenediamine.  If you're allergic to chemical hair dye and you use "herbal henna" you may to have an allergic reaction to the chemicals in it.  The claim of "no ammonia, no peroxide, all natural" does not mean you're getting safe, pure henna.

Want the good stuff without all the yuk?  Buy body art quality henna and mix it yourself!

Why your hair feels trashed and brittle after using synthetic dyes: Fia's Story


American College of Cosmetology
Standard Textbook of Cosmetology
Raritan, New Jersey, 1981

Amro, Bassam Izzidin
Dyeing with Henna and Related Materials
thesis for PhD at the University of Wales, 1989

Dalton, J.
The Professional Cosmetologist
West Publishing Company, 1976

Kenny, D:
Commercial premixed henna color treatments and conditioners, 
Cosmetics and Toiletries, 95 (6) 43, 1980 

Spanoudi,  S. P;
Henna, its morphology, chemistry, and hair dyeing properties
M.Sc Theses, UWIST, 1983

Wall, F.E.
Hair colorings, Bleaches, Dye removers
Chapter 23 in Cosmetic Science and Technology
2nd Edition, Vol. 2, Wiley Interscience, 1972

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