A researcher's accidental discovery could pave the way for a baldness cure by harnessing the power of white blood cells. The cancer expert was testing anti-inflammatory drugs on mice when she was surprised to discover they were growing extra fur, so investigated what was causing the phenomenon.

She discovered it was due to macrophages, which are derived from white blood cells called monocytes and are produced by the immune system to fight infections and clear up dead tissue.

According to Dr Mirna Perez-Moreno, who made the find at the Spanish National Cancer Research Centre in Madrid, the macrophages activated nearby stem cells which are responsible for hair growth.

That means follicles could be encouraged to grow without the need for a hair transplant, which can cost upwards of £5,000.

She and the study's other authors wrote in the journal PLOS Biology: 'One of the current challenges in the stem cell field is... to promote regeneration without the need of transplantation. Because of this study, it is now known that macrophages play a key role in the environment surrounding stem cells. Our study underlines the importance of macrophages as modulators in skin regenerative processes, going beyond their primary function as phagocytic immune cells.'

Previous research has identified signals from the skin that help prompt hair growth, but exactly how different types of cells do this continues to stir debate.

The study's authors believe their findings could also influence approaches to tissue regeneration, ageing and cancer.