For years, women have gotten cold rinses at hair salons in the hopes of making their hair shinier. The motivation behind this treatment is the commonly held belief that cold water ‘closes’ hair cuticles, making hair lie flatter and reflect more light. However, recent findings are soundly debunking this old wives’ tale.
According to chemists at TRI Princeton, an independent nonprofit scientific research organization founded in 1930, cold water has absolutely no impact on making hair look glossy. The researchers rinsed hair in water that was at least 98 degrees Fahrenheit (the hot group) or below 65 (the cold group), and eventually concluded that the hair rinsed in cold water did not have added shine. In fact, it’s the warm water that can do a better job of improving hair shine, as warm water can more effectively remove built-up residue from your strands.
Anabel Kingsley of the Philip Kingsley Trichological Clinic further explains this point to the website Into the Gloss, saying, “once the hair has grown past the scalp, it is technically dead tissue—it contains neither blood vessels nor nerves. Rinsing with cold water therefore has the same effect on hair as rinsing with warm water does,” she said.
Even Pantene, a leading haircare brand with its own research institute, says the cold water claim is totally unfounded. “There is a lack of scientific evidence to support this belief. Rinsing hair with cold water will certainly wake you up, but a scientifically proven (and much more comfortable!) way to make the cuticle smooth is to use the proper conditioner for your hair every time you shampoo,” Pantene writes in their Pro-Advice column.
Okay, so cold water isn’t going to give you the shine you once hoped it would, but can it actually be harmful? According to Kingsley, “rinsing with cold water can constrict the blood capillaries in your scalp. As these capillaries carry vital nutrients to the hair follicles, in theory, it may actually be harmful to hair growth.”
The bottom line: Cold water isn’t going to do you any favors, so you can stick to warm showers and rinses! In fact, here’s the healthiest temperature for your shower, according to science.