When she’s crouching behind her tripod, portrait photographer Emily Charais keeps her waist-length hair twisted in a knot, where it’s out of her way.

“I take pictures of people who spend a lot of time working on their look,” said Charais, who specializes in photographing ballet dancers. “I spend very little time thinking about mine.”

Still, the dancers she photographs might be surprised to learn that Charais, 34, hasn’t washed her light brown hair for three years — at least not with traditional shampoo.

“I have a really sensitive scalp and allergies to ingredients in shampoos. I’d used apple cider vinegar as a skin toner, so when I heard about using it on my hair, I gave it a try,” said the Marine on St. Croix mother of two. “Now it looks amazing. I rinse out the vinegar, and it smells good, clean — it doesn’t have that dirty hair odor.”

Charais is part of the growing no-shampoo (or “no-poo”) movement, made up of women and men who’ve given up the daily lather-rinse-repeat ritual. Their reasons vary, from concern about chemical ingredients and a desire to reduce the use of plastic containers to wanting to save money on hair care.

While some who make a clean break with shampoo just rinse their hair, most mix up alternatives from kitchen staples. A widely used method replaces shampoo and conditioner with a squirt bottle filled with baking soda mixed with water to remove the dirt, oil and smell. That’s followed by dabbing diluted apple cider vinegar on the ends of the hair.

The no-poo theory passed on by adherents and how-to websites suggests that shampooing strips the scalp of its natural oils, triggering it to produce even more oils. The counterintuitive premise holds that giving up the daily detergent wash will ultimately lead to less oily hair.

But Dr. Ronda Farah, an assistant professor in the dermatology department at the University of Minnesota Medical Center, said she’s seen no studies that validate such a “rebound effect.”

“Detergents in shampoo keep the hair and scalp healthy and clean,” said Farah. “If you don’t wash your hair, oil builds up and with that oil is dirt, sweat, dead skin cells and hair product.”

Perry Romanowski, a cosmetic chemist and co-founder of the Beauty Brains website, agrees. “Shampoos and conditioners work really well, but consumers always want something new, even when the products they’re using do the job,” he said.

Limiting hair washing is nothing new to those with textured or coarser locks. A number of websites devoted to African-American hair care have testimonials from people who have gone shampoo-free. And a growing number of people with curly hair are finding that less is more when it comes to shampooing.

“Curly hair doesn’t have as much natural oil on the hair shaft and is more susceptible to dryness. Cleansing agents can be too astringent and dry out the hair even more,” said Ebony Davis, a master stylist and educator at Intelligent Nutrients salon in northeast Minneapolis.

“A good rinse is often sufficient to get the dirt out,” she said. “Washing the hair every seven to 10 days is enough for most people.”

The international conglomerates that produce and market hair care products have been tracking the trend, and are responding by producing more shampoo options that are sulfate-free or labeled organic.

“There’s a growing subset of consumers who seek out naturally sourced products across the categories of everything they buy,” said Cecily Sommers, a Minneapolis-based global trend analyst and author of “Think Like a Futurist.”

“These are the people who want environmentally friendly options, whether it’s the food they eat or the household cleaning products they choose. Sustainable options resonate with their values.”

Earlier this year, Sommers gave up shampoo and now uses a cleansing conditioner instead.

“When I first heard about no-poo, I thought it sounded disgusting. Since then, I’ve known several people who’ve done it, so I decided to try,” she said.

But not everyone who is willing, or even eager, to toss out their shampoo finds success.

Lindsey Dietz figured she would be the ideal candidate to go no-poo.

“We live an organic and natural lifestyle. I make my own deodorant and toothpaste, and we use homemade chest rubs and herbal tinctures for health remedies,” said Dietz, 32, who lives near Silver Bay, Minn., and home-schools her two children. “If we can avoid the additives and chemicals in store-bought products, we try to do it.”

Dietz got off to a rough start when she began using the baking-soda-and-apple-cider-vinegar concoctions.

“At first, I couldn’t get a comb through it after I washed it. It felt like wet straw. Then it was a big greasy mess for a couple of weeks,” she said. “But after that, my hair looked great — soft, shiny, it felt good. I was telling everyone, ‘You have to try this.’ ”

But Dietz’s no-poo honeymoon ended a year later.

“I noticed it was getting dry, and it had a weird texture. It looked damaged,” said Dietz, who blogs about her family’s DIY lifestyle atTodayInDietzville.com. “The longer I went, the worse it got. Finally one day, I threw in the towel. I found products I felt were safe and weren’t tested on animals. Those are the products I still use.”

As chemist Romanowski pointed out, there’s nothing wrong with experimenting with hair-care approaches because few have lasting consequences.

“If something works for an individual, that’s all they need to know,” he said.

Kevyn Burger is a Minneapolis-based freelance writer.