Once avoided by fashionistas, beards and facial hair now have the endorsement of hipster and celebrity alike.

As George Clooney, Brad Pitt, David Beckham and even Ed Miliband embrace facial hair with fervour, thousands of hirsute east London-dwelling 20-somethings have followed suit.

And in the world of politics, if Jeremy Corbyn wins the Labour Party leadership he would become the first leader since Keir Hardie more than 100 years ago to sport a beard.

Facial hair remains the defining look for a generation of modern men and to coincide with World Beard Day today a university academic is launching a three-year project into the phenomenon.

Dr Alun Withey, an expert in medical history at the University of Exeter, is launching his study, Do Beards Matter?

He will examine facial hair and its relationship to health and hygiene in Britain between 1700 and 1918.

It was a period of extremes in facial hair trends - from the beardless Georgian era to the beard and moustache "movement", which began around 1850.

Dr Withey said: "Beards are as relevant now as they have been at any time throughout history.

"By looking back, we can understand that the current beard trend is actually just the latest in a long series of facial hair fashions.

"We can see facial hair not as some quirky irrelevance in history, but as a unique way of understanding the body, health, medicine and masculinity in the past."

The project will benefit from the input of an advisory board including the British shaving company King of Shaves and the Worshipful Company of Barbers.

It will survey a wide variety of sources to explore factors including the relationship between facial hair and masculinity, the role of medicine and medical practitioners in beards and shaving, and the impact of shaving technologies upon decisions to shave.

Dr Withey will examine how beard grooming evolved, from being a medical procedure undertaken by a barber surgeon in the 17th century, to becoming a daily part of men's personal hygiene routines by the Victorian era.

In the process he will survey a huge body of material from images, portraits and satire to personal sources such as diaries and letters to portraits, razor and shaving advertising and even the many theoretical and philosophical texts written about facial hair over the past three centuries.

Among the texts Dr Withey will study are Thomas Gowing's The Philosophy Of Beards from 1854, an article called Beards And Bacteria in the British Medical Journal of 1896 and a piece called Why Shave? in Charles Dickens' magazine Household Words in the mid-19th Century.

The fascination between beards and hygiene is longstanding and still relevant.

In May, a story generated by a small-scale study led by an American news channel went viral, after claiming that beards can be as dirty as toilets because they can harbour some of the bacteria found in faeces.

"This has been widely refuted," said Dr Withey.

"But it is interesting that remarkably similar claims about dirty beards have been made by opponents of beards for centuries.

"These sorts of stories highlight our continuing fascination with facial hair and the different 'looks' which can often come to define an age."

The project is funded by the Wellcome Trust.

"Personal grooming is a deeply relevant and crucial indicator of this," Dr Nicholas Vogelpoel, of the Wellcome Trust, said.

"This project will allow us to examine the resurgence of beard culture though an historical lens, bringing new insight to the unwritten history that is the evolution of our relationship to facial hair and what it means to be healthy and human."