The world is not exactly a sterile place: we're constantly surrounded by bacteria, fungi and viruses everywhere from our phones to door handles. However, researchers have discovered that they are collecting on our cash, and could be making us sick.
We already knew germs spread relatively easily through touch, whether we use the same doors, or shake hands with one another. We also pick up germs when we handle money.
Scientists have now discovered, however, that money doesn't just pick up and spread germs from person to person. It also picks up bacteria from any surfaces it touches. If you put cash through a vending machine, or it goes into a tip jar or till, it is picking up germs from the mechanism of the machine, the jar, the till, and the other money it nestles in beside.
And the bacteria and viruses lurking on cash, ready to spread, are horrifying. In fact, a separate study from Queen Mary University of London in 2012 found that 26% of bank notes and 47% of credit cards carry high levels of bacteria - and some carry more germs than the average toilet seat.
The researchers studied 200 notes and 45 credit cards and even found E.coli on some of the notes. Another study in Switzerland found that if a bank note is contaminated with the flu virus, it can survive on the note for up to 17 days, while the Novovirus can stay on a note for up to a fortnight.
The worst offenders are the £20 notes, because these last longer in circulation than smaller denominations, so change hands more and are carried around for longer, picking up germs.
The good news, however, is that plastic bank notes - like the new £5 and the forthcoming £10, are far cleaner than cotton notes. They are three times more hygienic, and bacteria is far less likely to survive on them. In the long term, therefore, our notes will end up less disgusting.
For now, at least, it's a good idea to wash your hands after handling money.