Do You Really Have to Wash Your Hair?

The so-called "French shower," that curious Napoleonic custom of applying perfume or deodorant over unwashed flesh, went out of style with pantaloons, and certainly never spread to these more hygienic shores. Right? Au contraire: Hello, dry shampoo. Touted as a water and timesaving way to stay quote-unquote gorgeous on the go, these wildly popular shampoo substitutes allow the busiest exec to head straight from the bedroom to the boardroom without a pesky shower in between. Just apply a cumulus of powder to the scalp, wait two minutes before brushing it out, and voila! Fabulosity achieved.

The market for dry shampoos, which are sold in both spray-on and powdered formulas, has exploded over the past few years. Name a high-end hair-care brand—Frederic Fekkai, Bumble and bumble, Oscar Blandi, Rene Futerer—and the chances are good that a revolutionary new dry-shampoo product is one of the top-selling items in the company's inventory. Their average price hovers around $20 for about 3 ounces—not exactly a bargain. So, how well do they work?

Old-fashioned wet shampoo cleans hair of all of the assorted gunk and free radicals that accumulate over the course of a day, as well as its natural oils, which are known as sebum. Dry shampoo, which usually has a base of talc, cornstarch, potato, or rice, soaks up rather than washes away sebum and dirt. When you brush out the powder, you're also (allegedly) brushing out the grime, too. Because the soak-up/brush-out method doesn't rid the hair of as much sebum, you can safely use dry shampoos once or several times between regular shampooings. But alert: Because dry shampoos are essentially spray-on powders, they can, even after vigorous brushing, lighten the crown of your head, which can be good or bad, depending on your desired hair color.

I spoke to a half-dozen dry shampoo devotees about their reliance on these potions. One "natural blonde" said dry shampoo helps her disguise suspicious roots on the brink of her next highlight appointment, since the powder tends to lighten the hair. Another turns to it when she can't submit to the 45-minute blow-dry required to tame her frizzy curls. (The New York Times ran a markedly pre-recession story last February on women who are accustomed to getting salon blow-dries every week and use dry shampoos to prolong the life of their high-maintenance styles.) Then there are the avid gym-goers who use it after midday workouts, and the partygoers who want to refresh their appearance in the office bathroom.

I recruited three testers with a range of hair types. Two are chemically enhanced blondes, one with thick hair and a schedule that only allows her to hit the gym during lunch. The second blonde has thin hair that looks flat and oily by the end of the workday; she'd prefer to take a second shower before any nighttime assignations. My third tester has thick, wavy, jet-black hair that requires herculean efforts to manage. All three work full-time and shampoo daily.

I, too, joined in. I have brown, straight, generally obedient hair that I never, ever wash on a daily basis, having been taught early on that too-frequent washing strips and damages hair over the long run. (And according to a recent NPR story, we Americans wash our hair way more often than is altogether civilized, averaging 4.59 shampoos a week, or twice as often as Italians and Spaniards.) Could the most ingenious of these products allow me to extend my alternate-day shampooing routine to every third day?

The candidates, from worst to best...

Klorane Gentle Dry Shampoo with Oat Milk ($18)