Purple Shampoo Is the Surprising Secret for Brighter and More Vibrant 'Brown' Hair

For years, we've been told that purple shampoo is for blondes and blue shampoo is brunettes — so much so that one became synonymous and exclusive to the other. The idea behind purple shampoos is that yellow is on the opposite side of the color wheel, and therefore, it helps counteract any brassiness. The same concept is applied to the blue shampoo theory.

However, it appears we've all been living in a lie.

Cynthia Alvarez, a Los Angeles-based celebrity hairstylist and Biolage ambassador, shares that brunettes can actually greatly benefit from using purple shampoo: "If there's any lightness to the hair at all, purple shampoo can help keep that tone cool. Even if it's very subtle babylights — using a purple shampoo religiously can really help keep any brass at bay."

Noted! But as with any treatment, it's important to know how often to do it for the best results. When using purple shampoo on brunettes, Alvarez says the frequency depends on your hair type and how much lightness is in your hair.

"If you're a brunette with a lot of golden ribbons, you may want to use your purple shampoo more often than someone who just has a touch of lightness," she says. "As a rule of thumb, I advise my clients to use it once a week — but you can adjust this based on your needs and how often you're washing your hair."

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There's some concern that certain purple shampoos can dry out the hair, which is why she recommends opting for a gentle, nourishing product instead. "The Biolage Color Last Purple Shampoo has a really low pH and is actually more moisturizing than your typical shampoo — so brunettes with more dry, damaged hair don't need to be afraid to try this product out."

And unlike with blondes, who sometimes get purple-tinted hair when they use too much, Alvarez says that brunettes don't face the same issue. "The purple tone will only get picked up on very light pieces of hair if left on for too long — think 20 minutes plus. If you do want to tone down the effects of your purple shampoo, you can just go in with a clarifying shampoo," she says.