Harry Styles dries his hair using a diffuser.

One Direction's hair stylist Lou Teasdale has dished the dirt on the boys' haircare regime, revealing that the cheeky singer's unruly mop of curls is achieved thanks to a hairdryer attachment which boosts his natural waves.

She said: ''The secret to curls is to let them dry naturally... if you need to get ready quickly, invest in a good old 80's diffuser attachment for your hairdryer. Not joking.''

Lou, who got her big break working on 'The X Factor' and 'Britain's Got Talent', also revealed she is trying to persuade Liam Payne to shave his hair off, but the 'Little Things' singer isn't too keen on the idea.

Asked if she planned to shake-up their style, the stylist told the Daily Mail's Femail: ''I would [like to] shave Liam's head again and grow Zayn [Malik]'s long again. I'm not winning on either.''

One thing Lou won't be trying out on the boys, however, is the new ''drainbow'' trend for faded rainbow-coloured locks, sported by the likes of Katy Perry and Demi Lovato.

She explained: ''Those cool people who live in East London were first on the scene with neon/lumo/vunge green/pink hair last year. And when the dye started to wash out, they accidentally created a whole new look: drainbow.

''It's a much more wearable colour trend that's great for girls who don't want to go too crazy with their pretty hair.''