Greasy hair can turn a first date into a last date, warrant painfully disapproving glances on the bus or, worse still, merit the nickname “chip pan”. So, why are increasing numbers of well-groomed women washing their hair only once a week? They have a secret weapon, of course – dry shampoo.

Well, perhaps, it’s not quite so secret any more. Boots reports a 45% rise in sales of dry shampoo in the past year, suggesting that, far from being an excuse to go all Swampy, the new generation of dry shampoos offers a practical alternative to a daily wash and blow-dry. Rumour has it that Miuccia Prada’s handbag is never without a trusty can of Bumble and Bumble’s Brown Hair Powder.

The concept may sound old-fashioned – you can imagine a 1950s housewife dousing her hairdo with a can of talc ahead of her weekly shampoo and set – but dry shampoos have grown up. Still produced with a talc base, they now contain refreshing and volumising agents, and work by mopping up excess grease from the roots and scalp, giving a matt finish that creates the illusion of clean, plumped-up hair. Simply spray your roots, wait a few moments for it to grab hold of the grease, then brush through to remove any chalky, white residue.

“There has definitely been an increase in the popularity of dry shampoos over the past year,” says the hairstylist Phil Smith. “My clients are always looking for timesaving products, and these are fast becoming a necessity.” For some, dry shampoo is a life-saver, eradicating the sins of the night before when a proper wash is simply out of the question. For others, it’s a chance to milk a professional salon blowout for a whole week.

There are other benefits to doing away with day-in, day-out washing and blow-drying: you will reduce heat damage and hang on to your colour for longer. Plus, after a day or two, hair is less fluffy and easier to style – ideal for creating fashionable retro dos, such as the Amy Winehouse beehive, that rely on a bit of grit for staying power.

In fact, Klorane Dry Shampoo was credited with helping stylists to create Kirsten Dunst’s deliciously powdered coiffeur in Marie Antoinette – a look that has since garnered its own underground following in clubs and on the burlesque scene.

But can this timesaver really substitute a proper shampoo and conditioner? “Ideally, hair should be washed on a daily basis,” says the trichologist Philip Kingsley. “Think how dirty your face gets at the end of the day – you can imagine how dirty your hair will be after a few days.”

He certainly sets out a convincing argument: even if the oil slick can be concealed, dirty hair still smells, and dry shampoos, whatever they promise, never leave you feeling as clean and confident as a good hair wash does.

Then there is the condition. “Washing your hair regularly is the single most effective way to get it looking and feeling its best,” says Kingsley. “Clean hair and a clean scalp mean healthier-looking hair.”

That’s as may be but, with time being like gold dust, surely it can’t hurt to have a wash in a can at the ready, should an emergency arise?

Spray away

Kevin Murphy Fresh.Hair, £12; www.hqhair.com
The handy travel size makes this one good on the go – ideal for a postflight or -workout overhaul

Klorane, £7; 0845 117 0116
The fresh scent makes this a favourite with celebrities and professionals alike

Bumble and Bumble Hair Powder, £27; www.hqhair.com
For hair artists and soap dodgers, with a can for every colour

Batiste Dry Shampoo, £2, from Boots
The original dry shampoo and the saviour of festivalgoers

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