Is Henna Good for your Hair?

 

I've been asked this question many times. Honestly, I've heard that henna causes your hair to become more porous over time. I've also heard that it causes your hair to be less porous! What is the deal?

What (Good) Henna Is

Colored "Henna" is usually derived from one of two plants: Lawsonia inermis (Red Henna) is the auburn reddish/orange henna and Indigofera tinctoria (Indigo or black henna) is dark. Most hair hennas are a combination of these two plants, with other additives such as walnut and/or rhubarb. Here's a great website with lots of information about henna: hennaforhair.com.

How Henna Works

Henna is considered to be a "deposit only" type of dye, because it doesn't interact with the melanin in the hair shaft. The way henna (Lawsonia inermis) works is that it imparts lawsone (hennotannic acid or 2-hydroxy-1,4-naphthoquinone) molecules into the hair shaft. These bind with the keratin in your cuticle. Keratin is found throughout the cuticle, but is concentrated in the innermost part of the cuticle. The longer the henna sits on your hair, the more molecules bind with the keratin, and the deeper the color becomes. The lawsone colorant sits above your natural color (melanin), which lies predominantly in the innermost cortex, deeper within the shaft. So the resulting color is a combination of your natural color (melanin) and the color of the lawsone molecules. Here's a GREAT article about the chemistry of it.

 

From Hennaforhair

If you want to dye your hair brown or black, you would add indigo to your henna. Indigo molecules sit mainly on the outer cuticle, as they are slightly larger than Lawsone molecules and don't penetrate as deeply into the cuticle.  The resulting color is the natural color of your hair overlain with the lawsone molecules, overlain with the indigo molecules. 

From Hennaforhair

What Henna Does to the Hair Shaft

According to everything I can find, henna coats the hair shaft, blocking holes in the cuticle and actually decreasing hair porosity.

The cuticle is the scaly outer covering of the hair shaft. The scales of the cuticle should lie flat, protecting the shaft. Chemical dyes work by forcing the cuticle open and pooling beneath them. The cuticles will not lie flat after they have been lifted like this, and your hair will feel rough. If the scales are continually lifted, they will break off, leaving weak spots, making the hair shaft thinner and more prone to breakage. 

Henna binds with the keratin in the cuticle without lifting the scales. Therefore, it does not cause this kind of damage. In fact, henna has been shown to actually improve the texture of the scales, causing them to lie flat, creating a moisture barrier. The shaft is actually thicker, smoother, and stronger when treated with henna.

 

Jacked up cuticle scales

Bleached hair shaft. The cuticle is rough and open, leaving the shaft highly vulnerable to damage. (pic from southlandsoap)

 

Chemically treated hair showing raised cuticle (pic from southlandsoap)

The same hair shaft after henna application. The cuticle is smooth and even. You can see the scales laying flat, which means that the cuticle is sealed. (pic from southlandsoap)

 

This is interesting. This shows the hair shaft coated in henna. You can see a light blue line above and below the hair in this picture. That's the henna coating! (pic from southlandsoap)

 

When Good Henna Goes Bad

BEWARE of commercially prepared "hennas." These are mostly "compound hennas" that come in a myriad of colors from blonde to black. These are mixed with chemicals, metallic salts or other dye plants added to henna to make any color other than red.  

According to Hennaforhair

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.

 

Conclusion

Use only natural henna. Avoid those heavy metals. 

Henna is awesome! Don't be afraid!