Mary-Kate and Ashley Olsen don't follow hair trends.

The stylish siblings - who are famed for their tousled tresses - like to make up their own rules when it comes to hair styles and cuts, according to their long-time haircare guru, Mark Townsend.

He told ''They have such amazing style, it is so inspiring. And it so personal. They don't follow trends -- they are usually setting them -- so they do what works best for them, what looks best on them and it's the same with their hair.''

The 27-year-old twins might have different go-to styles - with Ashley sporting long waves and Mary-Kate favouring a top knot - but they have both embraced the power of dry shampoo to achieve their laid back look.

Mark explained: ''They are blessed with having great texture and natural wave in their hair so we don't have to spend a lot of time to get that perfectly tousled look. The biggest secret is the dry shampoo - it gives the hair such amazing texture.''

The stylist - who is also in charge of Lea Michele and Jennifer Lawrence's locks - revealed the secret to keeping the girls' blonde hair in good condition is a special blend of natural oils.

He said: ''I recently made up a conditioner for the girls ... and told them to put it in their hair before swimming and while in the sun; it was coconut oil, almond oil, jojoba oil, and vitamin E. All things I picked up at the health food store!

''When they got back, they both asked me for more and I could feel a huge difference in their hair. They use it a couple times a week and leave it in for up to an hour.''