Last year, a group of 200 women in 40 states filed a class action lawsuit alleging the cleansing conditioner from Wen by Chaz Dean caused scary side effects, from scalp irritation to hair loss.

On Oct. 31, a federal judge in Los Angeles gave preliminary approval to a $26.3 million settlement for the suit against celebrity stylist Chaz Dean and Wen distributor Guthy-Renker. If approved by a United States district judge, customers who had adverse reactions could receive up to $20,000.

Wen is a leader in the no-shampoo movement. Many women believe that conditioner washing or "co-washing"—using only cleansing conditioner (and no shampoo)—makes their hair feel healthier, softer, and easier to manage.

But the women represented in the lawsuit say they've had the opposite experience: They claim Wen's cleansing condition caused "severe and possibly permanent damage to hair, including significant hair loss to the point of visible bald spots, hair breakage, scalp irritation, and rash."

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"From what we understand about the product and how it causes hair loss is it contains virtually no cleanser," attorney Amy Davis told CBS. "It’s like using lotion to wash your hair. So instead of removing the product when you rinse it off, it just becomes impacted in your hair follicle."

The hair-care brand is standing by its products. "Wen by Chaz Dean is safe and we continue to provide our hundreds of thousands of customers with the Wen by Chaz Dean products that they know and love," the company said in a statement. "Since the process of litigation is time consuming and costly, we made a business decision to pursue a settlement and put this behind us so that we can focus on delivering quality products."

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So, should you hesitate to use a cleansing conditioner like Wen's?

This question is a tricky one, in part because experts haven't been able to figure out what, exactly, caused the concerning side effects. When we asked two dermatologists about the lawyer's description of the Wen product becoming "impacted" in the hair follicle, they both agreed it didn't make much sense.

"I'm certainly not a legal expert," says Debra Jaliman, MD, a dermatologist in New York City. "But since hair grows from the hair follicle—which is under the skin—and not from the surface, I couldn't really make sense of this lawsuit." What's more, she says, if a product doesn't contain any cleanser, the result would be oily hair: "I can't see how it would cause hair loss."

Mary Gail Mercurio, MD, an associate professor of dermatology at the University of Rochester Medical Center, says the worst side effect she'd expect from a cleansing conditioner would be oily, matted hair that feels weighed-down. "I'd think it might have a negative effect on appearance, but it shouldn't cause breakage," she says.

Both doctors felt the lotion analogy Davis used was puzzling, since washing your hair with lotion shouldn't cause your hair to fall out either. "Dermatologists often prescribe medicines of varying viscosity for the scalp without seeing this phenomenon," says Dr. Mercurio.

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But could the Wen formula contain some kind of depilatory that's causing the women to lose their hair? Unlikely, according to Dr. Mercurio. "If there were a specific depilatory ingredient in these products, it would affect more women," she points out. "There are many causes of hair loss. It's possible that some of these women are sustaining hair loss from a separate issue."

What about the no-shampoo movement itself, we wondered—is there any risk to skipping shampoo?

There's no "right" frequency for washing your hair, the experts say. "It's a very individual thing," explains Dr. Mercurio. "It really depends on scalp's oil production, which differs from person to person."

In other words, it's up to you to find what works best for your hair. While some people don't like the feeling of unwashed hair, others swear by the “no ‘poo” approach. In fact, Health executive deputy editor Jeannie Kim experimented with only co-washing her hair for one month last summer. She loved the results so much, she hasn't used shampoo since.

"I’m now at 15 months and counting of using only cleansing conditioner, even after pool swimming and major sweaty workouts," she says. "I do make sure to massage my scalp really well, both with the product and after rinsing to make sure I’ve gotten it all out."

For now, it seems the best advice is to experiment with co-washing, but cautiously. As with any hair- or skin-care product, watch for unusual symptoms and discontinue use if you experience a negative reaction.

This article originally appeared on Health.com.