Why Swimming Pools Turn Hair Green (It's Not the Chlorine!)

Are your light-colored locks destined to go green this summer? (Photo credit: Stocksy/Jovana Rikalo)

Chlorine is commonly assumed to be the culprit behind Kermit-colored hair. But the truth is, another compound designed to keep the pool clean may actually be what’s turning your hair green.

Copper sulfate is often added to swimming pools to combat algae, according to the authors of a 2014 case study about a 15-year-old girl whose blonde hair was turning progressively green. “Copper compounds in the water bind to the protein on the surface of the hair shaft and deposit their color,” the researchers explain. (This can also occur if your home has new copper piping.)  

Although blonde hair is the most likely shade to go green, “it happens to other colors also,” says Steve Pullan, a trichologist at the Philip Kingsley hair clinic in New York City. “You just don’t notice it as much.” As a hair scientist, he sees green-haired goddesses all summer long — and has noticed a trend among these clients: They’ve often bleached their tresses.

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“Even natural hair can become green,” Pullan tells Yahoo Health. But coloring your hair — especially when bleach is involved — makes the shaft of each strand more porous, allowing your locks to absorb the pool chemicals more easily. In fact, in a study called “The Green Hair Problem,” conducted way back in 1979, researchers found that hair treated with peroxide or damaged by the sun was more likely to suck up copper.

To shield your strands, soak them with fresh water before diving into the pool. That way, “the hair is already wet, like a sponge,” says Pullan. The result? It’s less likely to absorb the copper-tinged pool water. Even better, wet your hair and coat it with conditioner before swimming. Pullan recommends Philip Kingsley’s Swimcap Cream, originally developed for the U.S. Olympic synchronized swimming team — it contains sunscreen to shield your hair from UV rays, while also creating a protective barrier against copper. Afterward, rinse off in the pool shower to eliminate any lingering chemicals.

Related: U.S. Swimming Pools Ban Long Breath-Holding After Deaths

Still have a green-hair mishap? You may be able to mask the funky hue with a shampoo formulated to prevent gray and blonde hair from going brassy, says Pullan. In addition, “we deep-condition to lift out impurities and cleanse the scalp very thoroughly,” he says. You can also try a chelating shampoo — that is, one capable of stripping away mineral-build-up — such as Redken Hair Cleansing Cream Shampoo.

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