Oil production is hormone-based, said Hansen. He encourages people with oily hair to wash more frequently so their hair looks and feels better. People with dry hair can wash less often.

"It doesn't make a lot of sense to me," he said about the no-poo method. "I don't know if there's any reason that would make it a bad thing to do, but I don't think it would be as effective for what you're shampooing for, which is to clean and make your hair more manageable."

In the Salt Lake Community College's barbering and cosmetology program, students traditionally use baking soda to strip hairspray or other buildup out of a person's hair, said Susan Curtis, an assistant professor. Vinegar is used to remove excess soap build-up from of a person's hair.

"I've never heard of people mixing the vinegar and the soda to wash," said Curtis, laughing. "You'd have Vesuvius. That's the mix you use to make a volcano."

But no-poo followers say they are careful to rinse their baking-soda scrub before adding vinegar to their hair.

From Curtis' perspective, it is important for people living in Utah to replace the natural oils in their hair because of our dry climate. She advises people in this state use a deep conditioner once a week.

Her colleague, Brenda Matern, said she worries that a person using baking soda could strip too many of the natural oils out of their hair. As for how often a person should wash, she said it is personal preference.

"Some people say not to wash your hair every day," she said. "I wash every day."

Moore, on the other hand, advises clients with normal hair to shampoo every other day. For people who say they "have to" wash every day, she still recommends shampooing every other day, but then rinsing and conditioning on the off day.

But no matter how a person washes their hair, Moore advocates it be done regularly.

"You must consider that your head emits natural oils, and a buildup of this oil also means a build-up of pollutants from the air, sweat and bacteria," said Moore. "Washing on a regular basis is healthy and generally recommended."

With the no-poo method, people generally go through a two-week transition period when their hair feels dirty and greasy, according to Moore. But after that, oil production slows, and they will feel their hair become more balanced and normal.

Christi Colvin wrote in a recent blog posting for www.naturemom.com that she loves what no-poo does to her hair.

"I have straight-as-a-board, baby-fine hair that has never held a 'do,' " she wrote. "After no-poo, I don't even have to use styling products. I just blow dry and go; my hair now keeps any style."