But does a rinse with cold water really matter though? At the risk of gaining the ire of a worldwide population who’ve all grown up gritting their teeth for the promise of sheen like a baby seal’s, we asked Unilever’s resident R&D expert, Leon-van Gorkom, to get to the bottom of things. Read on:

Should We Really Rinse with Cold Water for Smooth, Shiny Hair?

“The only benefit that people have [from this] is that it closes the cuticle,” Leon says. Which is actually the case, either way you turn that dial: “The cuticle will close itself anyway; it’s just more comfortable to rinse in the shower with cold water,” he adds. “We don’t say rinse out with hot water, because hot water will dry out your scalp and it will dry out your skin.” So what about all those instructions, those countless bottles of conditioners that have instructed us to rinse with cold water for shinier hair? Take things with a grain of salt, Leon advises. “In real life, whether you rinse with lukewarm water, mildly hot water or cold water, the end result is going to be the same. Once hair is dry, the cuticle is going to be closed [anyway], so the end benefit, whether you rinse with cold, lukewarm or warm water—you can’t tell the difference.”

But—it’s also not just your imagination

That certain slip you get after rinsing hair that’s been conditioned is still there, but more as a result of the product and not the water’s temperature. “When hair is wet, whether it’s [with] cold or lukewarm water, the swelling happens because water is there, and not from what temperature the water is,” Leon confirms. So take this as your official PSA, ladies: Go with whatever makes you feel comfortable. Some people love the jolt from a cold shower, others not so much. Personally, I love a warmer rinse, and will be relishing in my newfound icy-free existence. As for broccoli… I might have to do a bit more research on that! Want more hair care tips you can do in a jiffy? Check out these hair hacks perfect for weekday mornings.

Shinier Hair Via a Rinse with Cold Water  Fact or Fiction  - 24