Henna has had a recent resurgence in the use of hair colouring and I was also pleased to read it is being looked at more closely in textile dying as it is a less-toxic approach to filling our lives with colourful cloth and yarn. Although a natural dye it does have its challenges for both the Professional Stylists and consumer, so due to popular demand I have put together this blog which looks at henna and some of its challenges.
The Henna plant (Lasonia intermis) is a tall shrub or small tree growing up to about 2.6m in height It is mostly found in African, Southern Asia and Northern Australia; yes, it likes heat. The leaves are the part that is used to create the dye used on the hair and skin. The white, extremely fragrant flowers are used for perfume and for essential oil extraction. Although it has not yet found its way into modern medicine or scientific testing, henna has a firm place in traditional medicine, where nearly all of its parts are used including the berries and bark.
I discovered while working in Indian many families plant henna in the garden to keep a regular supply. I was also surprised to witness just how many people of all ages use henna in their hair and and on their bodies, then I discovered that it helps with UV protection and dandruff to name a few of its claimed properties. A difficult argument in the Wella Studio Delhi when models presented themselves and I had to ask that they let the henna grow out or we could not accept them as colour models. More about why later in the blog.
Henna itself is an orange dye that is achieved when the leaves fresh or dried are pulverised. To activate it must be mixed with a mild acidic fluid e.g. lemon juice, to create a paste around a pH of 5.5 that needs to sit for around 8 hours, only then are the Lansome molecules (2-hydroxy-1, 4-naphthoquinone) available for dyeing. There is still a chemistry involved with natural products, during the time the henna sits in the lemon juice it starts to transform so that when you put the paste onto the hair or skin the Lansome molecules about the size of amino acids migrates from the paste into the keratin binding permanently to leave a red-orange stain. The action is similar to putting a wet tea bag on a cotton tea-towel; the longer you leave it, the darker the stain. Six hours is generally enough for maximum absorption. Even when washed off the Lansome molecules bound in the hair will continue to develop and oxidise resulting in a more vivid or intense result over the course of a week. Yes! it is a permanent stain; the only way to remove it is to grow it out of the hair, it will fade slightly over time but it will not fully wash out. It is also permanently dyes the skin but as skin renews itself every 30 days or so it the colour skin will shed off.
While natural henna is generally a red-orange colour, variations in result do exist. These variations usually contain ingredients from other plants and even synthetic dyes. Indigo is natural dye from a plant (Indigofera tinctoria, suffructicosa, or arrecta) that can be added to henna or layered on top of it to create brown to black colours in the hair. All you colour experts will know this from the colour wheel, henna being orange, and indigo blue are complementary colours, the two colours working together create a variety of browns and neutral tones. Unfortunately, the Indigo dye is not as stable as henna and can fade leaving the henna more prominent if not applied regularly.
These are after all-natural dyes and each one is unique, the challenge for upscaling and manufacturing is preserving, once cut from the plant the leaves will start to decay, even when dried the effectiveness has a relatively short shelf life. I did read several years back a patent L’Oreal were working on to allow Henna and Indigo to be effectively processed and stored which would result in a more unadulterated product which I see they have launched under their Matrix Biolage Hair Color 82-100% natural. Wella have had on the market for over two decades their Natural Hair Colour called EOS which has some direct-acting dyes mixed with henna to allow for a greater range of shading. Henna and indigo based natural colours are available from big manufactures and these companies are very clear about what is in the product.
This is where it starts to get more uncertain, there are many claimed ‘henna’ products available in the market place, but there are no regulations as to what constitutes a henna colour. The challenge lies in the ingredients; if you want to understand more about INCI ingredients click here. Not all ingredients are listed and even claims such as organic are questionable as each market defines what organic is. Many of the henna products I have looked at contain dye-stuff such a PPD (paraphenylenediamine) that can over time increase users’ risk of an allergic reaction or older dyes no longer allowed for a variety of reasons from safety to unsustainability. Not one to shy away from any dye-stuff the issue for me as a product developer and Professional is that all of these mixed versions of henna do not carry the warnings or skin test advice that all users should be aware of and carry out before use.
But why is henna to hairdressers as garlic is to vampires, it is after all a natural product. Simply, it is the uncertainty. It is permanent in the hair and during regular applications the henna is applied all over which results in an uneven density of staining and porosity (it will affect porosity). The permanency is achieved in how the henna bonds to the hair fibre, this staining action is different in how our natural colour and artificial colour works. Our natural and artificial hair colours work by placing small molecules of colour within or on top of the hair. We simply cannot get at the henna it goes where our chemistry does not. The difficulties become obvious when you want to go lighter. Whether you use a colour or bleaching product, the henna will remain and the finished result will reflect a strong uneven orange-yellow tone. This is why I recommend clients who have used henna to stop and let it wash/wear out of the hair. The same way in my earlier example of the tea stain on the cotton tea-towel, it will gradually fade to a point it is less noticeable. I do take regular strand tests to assess progress. In contrast going dark is not going to be as challenging although the warmth from the henna will be ever present.
Having said all that, there is an assumption that the henna used was pure which was the case with models and clients in India. But, yes, there is a ‘but’! If the henna is not pure it will not only stain the hair but will impart other substances into the hair like the previously mentioned PPD or anything else that has been added to fill out, preserve or improve performance. It is the other stuff that is the greatest concern, especially when working with a reactive chemistry; perming, straightening, relaxing, and oxidative colouring. These chemistries exchange their chemistry with the hair’s chemistry and any other substance in the hair. We know how the hair’s chemistry will react, anything else is the great unknown and as such the reaction is also unknown. These extreme reactions you tend to read, hear or if unlucky witness; radical reactions such as smoking, swelling, separating and over-heating of the products applied can cause hair and skin damage. All of this can be avoided by taking a strand test and apply the products you are in intending to use. If in doubt don’t apply anything except a non-reactive chemistry such as a direct-acting dye.
I do like the introduction of natural dyes into the world of hair but it needs to come with education and regulations to ensure the quality of what is in the powder. However if we start to include truly natural products into Professional hair we and our clients will need to change mindsets, after all if it is natural there will always be variances in delivering consistent results, e.g. the Henna Lawsone molecule concentration can vary greatly depending on when it is harvested and the quality of the leaves themselves; the greener the leaf the higher the Lawsone concentration. A bit like wine, some years the yield and products are award winning and other years they are just average.
And in case your wondering, yes I did use henna on my hair for almost 1 year Wella’s earlier version of EOS called Living Colors and I loved the look and feel of it, the only downside for me personally was that it limited my other choices. After all like many a hairdresser I loved the chance to try out different hair colours.
Caroline
If you would like to read a little more into henna and hair, I found this blog with a free book on the subject Ancient Sunrise® Henna for Hair by Catherine Cartwright-Jones, PhD
