Hairdresser Lee Stafford, whose celebrity clients include actress Billie Piper and model Agyness Deyn, says: "Dry shampoo is phenomenally popular, but it's not designed to be used on a regular basis.
"It contains an oil-absorbing substance to soak up the grease, but if it's used constantly it's going to dry out the hair and the scalp and make it flaky. If it's left on the hair too long it can also clog up the pores, leading to spots and sore patches."
This is exactly what Kerry Kilmister discovered when she began using dry shampoo regularly after giving birth to her third child, Poppy, now five months. Like many busy mothers, Kerry, 34, from Chippenham, Wiltshire, found herself with little time to spend on her appearance, and turned to the product as a solution.
"After Poppy was born, I didn't have time to wash and dry my hair more than once a week," she says. "I thought my can of dry shampoo was an easy fix, and I started using it every day.
"I loved the way it made my hair look less greasy, gave it a nice smell and added volume.
"After a few weeks, though, I noticed my scalp was getting itchy and sore. I started getting bad dandruff, and then I developed little sore patches on my head, which would catch on my hairbrush and bleed.
"It was horrible, but I didn't connect it to the dry shampoo. It was my hairdresser who told me I was using it too much."
Kerry has stopped using the product entirely, and the flaking and soreness has cleared up.
Though it's very much in vogue, dry shampoo isn't a new concept. The Victorians used to sprinkle arrowroot powder on their hair to absorb the grease.
Commercially available dry shampoos appeared in the Sixties and Seventies, with the U.S. brand Psssst! among the first.
Modern versions, which range in cost from £3.99 (NZ$9) to £28 (NZ$65) for upmarket Bumble and Bumble's hair powder, have moved on.
They are less chalky, come in a number of coloured shades and contain volumising agents that make it as much a styling product as a shortcut.
But in many respects, they work on the same lines as the earliest versions. The problem is that dry shampoo isn't shampoo at all: it doesn't clean the hair; it simply deposits a substance, such as talc, corn starch or rice starch, on the scalp to absorb the oil.
"It's the human equivalent of the dust baths animals take," says Iain Sallis, a trichologist at the Farjo Hair Institute in Manchester. "It coats the hair rather than making it clean, which means that the microbes which feed on the moisture in the scalp will still be there.
"For people prone to dandruff or dermatitis, the scalp will become flaky to get rid of the irritation.
"And by its nature, it's a gritty product, which will cause friction on the skin. That can make the scalp sore over time, especially if it's not washed out."
Jonathan Long, co-founder of top London hair salon Lockonego, whose clients include Sienna Miller and Pippa Middleton, agrees.
"If you applied excessive amounts of make-up to your face without washing it, your skin would become congested and irritated. It's exactly the same for your scalp."
Kym Fryer suffered dermatitis as a result of over-using the spray. Her reaction was so severe that she developed bald patches.
Kim, a 35-year-old teacher from Leeds, says: "I'm so busy in my job that when I discovered dry shampoo a couple of years ago, I started using it every day. Over time, I developed a red, scaly rash around my hairline, which I put down to stress. Then, one day my mum spotted a bald patch at the back of my head, which horrified me. My hair had started to feel dry and brittle."
Four months ago, Kim's hairdresser commented on her rash and the bald patch. "She told me to stop using the dry shampoo, because it was obviously irritating my scalp. I've never used it since and thankfully, my hair's grown back," she says.
Hair loss, a common complaint from dry shampoo users, could be the result of shedding a large amount of hair in one go rather than incrementally, as those who wash their hair regularly will do.
Trichologist Iain Sallis recommends using dry shampoo once a week at most.
"It won't do you any harm if you use it occasionally, when you really don't have time to wash your hair," he says.
Jonathan Long believes that as well as a quick fix every now and then, it is best used as a styling tool for clean hair.
"It's great if you're trying to style your hair and it keeps falling out of the style," he says.
Virtually all celebrities with big hair - including Jennifer Aniston and Kate Moss - have relied on dry shampoo at some point to give their hair va-va-voom volume and help up-dos stay in place.
When it comes to using dry shampoo without suffering adverse effects, as Iain says, the main rule to remember is: "It's fine, as long as it's an "as well as", not an "instead of" proper washing."
Bad news for the lazy or exceptionally time-pushed among us, but good news for the health of our hair.
- Daily Mail
