A survey of women in the UK has revealed that one in 20 admit to having gone 10 days without washing their hair.
The poll also revealed that millions of busy women rely on 'hair hacks' like dry shampoo or scraping their barnet into a bun to save time on washing their locks.
Over a third of women use spray-on shampoo and similar products to keep their hair looking fresher for longer.
Other short cuts include putting it in a ponytail or a plait - or simply hiding it under a hat.
The poll, commissioned by Herbal Essences shampoo, took in the responses of 2,000 UK women, aged between 18 and 40.
Spokesman Ben Cooke said: "We all know it's important to keep hair clean and refreshed but sometimes we forget about how much it goes through every day.
"Women's hair care regimes are very important and very personal - so what works for one person may not work for someone else.
"We thought we'd find that most women had similar approaches to keeping their hair clean, but the results actually showed a wide variety of methods."
A fifth of women wash their hair daily, but on average women in the UK do it every 2.6 days.
Six in 10 respondents said they only really feel their hair is clean if it smells nice.
And four out of five agreed with the received wisdom that "washing your hair every day will strip it of all its natural shine and oils".
Ben Cooke added: "Pollution and weather on top of hair styling can make hair feel like it needs a detox, even after just one or two days."