If you need to lighten or bleach your hair, right now there's no chemical-free way to do it, though plenty of sun exposure should help. But if you want to change or enrich your hair color and cover grays, there are lots of herbal and plant-based options.

These alternative hair dyes have become popular because the ingredients in conventional dyes have come under increased scrutiny. Some people develop allergies to the chemicals in hair dyes — the stories online are numerous, and include plenty of scary skin-burning or hair-falling-out narratives. Others are concerned about certain ingredients in hair color, especially p-Phenylenediamine (PPD), potentially being carcinogenic and mutagenic. According to the Campaign for Safe Cosmetics:

Aromatic amines found in hair dyes...are linked to increased incidence of bladder cancers. However, studies looking at the risk of cancer associated with the use of hair dyes have returned conflicting results and the International Agency for Research on Cancer (IARC) states that it is unable to classify the carcinogenicity of p-phenylenediamine.

When P-phenylenediamine reacts with hydrogen peroxide, as it does in the preparation of hair dyes, it can form a mutagenic, or DNA-altering, substance called Bandrowski’s base. Bandrowski’s base has been shown to be strongly mutagenic and possibly carcinogenic. It is clear that there is a high potential for consumer exposure to mutagenic substances when using oxidative hair dyes.

Blackcurrant

In the U.K., blackcurrant is being investigated as a future hair-coloring agent. After the delicious flavor of these berries is extracted to make Ribena (a popular British fruit drink that offers vitamin C and antioxidants), there's plenty of plant material left over. Some scientists are figuring out a way to make that waste into a natural hair color.

University of Leeds color chemist Dr. Richard Blackburn and organic chemist Professor Chris Rayner published a recent paper on the subject in the Journal of Agriculture and Food Chemistry.

“Anthocyanins are pigments that provide colour to most berries, flowers, and many other fruits and vegetables. They are non-toxic, water-soluble and responsible for pink, red, purple, violet, and blue and colours and are widely used as natural food colorants all over the world. We knew they bound strongly with proteins – hair is a protein – so we thought if we could find an appropriate source of these natural colours, we might be able to dye hair," Rayner told ZME Science.

The scientists have successfully created red, purple and blue hair colors that last as long as conventional dyes on hair (mixed with yellow, they can get a range of brown tones as well, all from blackcurrant left over after food processing).

Henna

I'd love to try blackcurrant on my hair one day. For now, I'm using henna. I stopped using conventional hair dyes about five years ago when I learned about the possible health implications. I have been pleasantly surprised by a side effect when I turned to henna: Forgive me if I sound like a late-night TV advertisement, but my hair is longer, stronger and thicker since I quit using chemicals. From about age 20 to 35 I used all manner of expensive and inexpensive hair dyes and I thought my inability to grow my hair past my shoulders after my mid-20s was just a sign I was getting older.

But five years into my henna-only dyeing adventures, my hair is almost down to my waist. My hair feels "happier" to me. It's a lot less frizzy too, so overall I not only wash my hair less, but I use much less hair product. I wish I had always dyed my hair with henna.

Here we go!! #thisis40 😮😱😮😱❤🦄🌈😎

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Henna comes as a powder made from the leaves of the Lawsonia inermis plant and has been used to color hair and skin for thousands of years. It works by blending with hot water to turn it into a paste and from there goes on like any other dye would. Henna is often used to color hair red, but there are plenty of other shades, including neutral (if you just want a gloss) and browner tones. You can also add to your base henna to change the color slightly — I sometimes use red hibiscus tea instead of plain hot water when I'm mixing up my henna for a little extra brightness. Some use coffee to tone down the red tones. I recommend mixing your henna with coconut and olive oils when you add the hot water so as not to dry your hair out during the dyeing process. Some people recommend mashing up an avocado — any natural plant oil will probably do the trick to get moisture into your hair while you color it.

Now that I have plenty of white hairs surrounding my face, I can personally back up the claims that henna makes about covering grays — it definitely covers the white streak that's developing around my face. Unlike a conventional dye though, henna won't dye your hair one even color, so my whites look like lighter highlights of the red of the rest of my hair. I like this look since it makes my hair look like it has more variation in color and tone, just like undyed hair usually looks. (Conventionally dyed hair can sometimes look flat because it's all one color.) Henna looks wonderful in the sun. And yes, henna is suitable for all hair types and textures and people of every background.

One caveat, however, if you don't like the way henna looks, you can't easily go back to traditional permanent hair dye. Some hair stylists recommend waiting until all your henna-colored hair grows out and only touching up your hair with semi-permanent dye in the meantime.

Indigo

I have a newfound appreciation for cloth and the fibers that clothe me. Hand woven cloth is one of the most sustainable fabrics you can find. It's made by human hands, not machines. It's also softer, more luxurious and supports a generational craft that's threatened by fast fashion. Since 2003, @indigohandloom 's work has supported artisans and handloom weavers in rural villages of India. I take pride wearing cloth, in natural materials, that help an artform live on. The feeling beats the impulse buy high of a $10 scarf any day. Invest in fewer, better things. . #artisan #indigohandloom #zen #stripes #teatime #sustainable #ethicalfashion #clothe #consciouscloth #textiledesign #textilelove #madeinindia / photo by: @jenmay.cr2

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You might think of indigo as the plant that colors your dye-your-shirt-at-home projects, or has gone into making your jeans, but it can also be used as a hair-coloring agent. Used to color hair black, it was so popular in the 19th and 20th centuries in the U.S. and Europe that it was often referred to as "black henna." (Henna can't be black but indigo is another plant that can be used as henna is to color hair.)

Andrea Plell, an ethical fashion consultant and cofounder of the Sustainable Fashion Alliance, uses a combination of indigo and henna on her dark brown hair in the form of Lush’s Caca Marron henna. "I always get compliments on not only the shade of my hair but how healthy it looks. It's also much more voluminous than it used to be. I’ll never go back!" says Plell. Lush's henna comes in blocks that are premixed with fair-trade cocoa butter and essential oils so you can break off how much you want to use and it stores easily.

It takes some time

applying henna to a woman's hair Natural products typically take much longer to work than traditional dyes (and are just as messy!) (Photo: AFPics/Shutterstock)

Yes, natural products do take longer to "develop" on the hair — three hours is the typical recommendation. The upshot is that you can do it at home, so it's less expensive, and you don't have to make an appointment or travel to the salon. (Some salons do work with henna, so try Googling it.) But three hours is definitely longer than the 30 to 40 minutes conventional hair dyes take. I tend to apply my henna in the morning after I've worked out, then leave it on much of the day while I work. You can't hurt your hair by leaving henna or indigo on for "too long" — some people even sleep with their heads wrapped up and leave it in overnight. "I’ve transformed the 'waiting time' into a self care ritual that I look forward to every few months," says Plell.

Henna and indigo last as long as any other hair dyes (I've tried them all!) in that they fade a bit over time, and you will need to touch up your roots when they grow in, of course. I've found I can go 6 to 7 weeks in between applications and I do a full-head dye every other time and a roots touch-up otherwise. If you're at all curious, give the natural alternatives a try; I'm saving so much money and my hair is significantly healthier from using them. And I'm not dumping possibly hazardous chemicals into my local water supply when I rinse the plants from my hair, either. It's a win-win-win for me.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.