Think twice before eating those dropped crumbs off your computer keyboard -- you might as well be eating off a toilet seat, according to a new study on the amount of germs on keyboards.

A study by British consumer magazine "Which? Computing" asked a microbiologist to examine for bugs on 33 keyboards in a typical London office, a toilet seat and a toilet door handle.

Four keyboards were judged potential health hazards and the microbiologist recommended the removal of one keyboard as it had 150 times the pass limit of bacteria -- five times filthier than the swabbed toilet seat.

"Most people don't give much thought to the grime that builds up on their PC, but if you don't clean your computer, you might as well eat your lunch off the toilet," said Sarah Kidner, editor of "Which? Computing" in a statement.

The study found that eating lunch at desks is the main cause of a bug-infested keyboard. Dropped crumbs and food encourages the growth of millions of bacteria.

Poor personal hygiene, such as not washing hands after going to the toilet, may also add to the dirtiness of keyboards.

But despite the health hazard of a dirty keyboard, a survey of 4,000 people by the magazine found one in 10 people ever cleaned their keyboard while another two in 10 never cleaned their mouse.

Almost half -- or 46 per cent -- cleaned their keyboard less than once a month.

To clear out bugs, the magazine recommends users unplug keyboards, turn them upside down and shake them.