The Trichological Society says a growing number of salons are offering to do them at a cheap price and some hairdressers don't have the qualifications to put them in properly.

The organisation says that's leading to more young women suffering from hair problems such as bald patches and alopecia.

Barry Stevens is a hair scientist who runs the group.

He said: "People who have hair extensions usually have high hopes they'll look and feel good but very often it ends in tears.

"There can be quite serious consequences wearing them for a long period. They are capable of destroying hair permanently."

A report published in the British Journal of Dermatology also warns people about the possible dangers of hair extensions.

Researchers in the US and Italy say problems with them are more common than reported.