Clean charts the long history of our attempts to keep body and soul spick and span. According to Virginia Smith, our desire for cleanliness goes back to "our very 'Neolithic' love of grooming, orderliness and beauty". Keeping yourself clean may be a survival mechanism but, as with everything, Homo sapiens has turned necessity into an art - and even a religion. The Greeks gave us bathrooms and the word hygiene, originally meaning "wholesomeness and human healthiness". Then there was a whiffy interlude while the ascetic Judaeo-Christian tradition tried to convince us that a pure soul was more important than a clean body. Thankfully, Greek hygiene won the battle of the bathrooms; but have we now become too clean? Some say the rising incidence of allergies may be due to a lack of wholesome dirt when we're young. At times Smith struggles to fit such a vast subject into one book, but this is a fascinating cornucopia of cleanliness. Did you know that 80% of vacuum cleaner dirt is human skin cells? Yuk.