As a result, many women are left with permanent bald spots because the damage to follicles is irreversible.

Even women who had no visible signs of hair loss after wearing extensions had considerable underlying damage to the scalp when examined more closely, dermatologists from the University of Miami in Florida in the U.S. and Bologna University in Italy found.

Fears over the growing use of extensions first hit the headlines two years ago, when Victoria Beckham was photographed with a sizable bald patch after years of sporting false hair.

Kate Beckinsale, Christina Aguilera and Britney Spears have also all been spotted with thinning hair after using extensions.