If you have young children, you should consider asking your guests to take their shoes off at the door, an expert has said.
Many people demand a shoe-free home for cleanliness reasons above anything else.
But studies show that shoes are home to many bacteria, some of which are a health threat if consumed in large amounts.
Children crawling around on the floor are at most risk of picking up these germs, according to Dr Jonathan Sexton.
He told Live Science: 'For a healthy adult, it's not too big of an issue. I'd be more worried about a child crawling around on the floor.'
Dr Sexton is an environmental microbiologist and research specialist based at the University of Arizona.
Studies have found bacteria, including faecal matter, which can cause dangerous infection or illnesses, on the bottom of shoes.
The average shoe harbours 'hundreds of thousands of bacteria per square inch', other scientific trials have shown.
Shoes can be contaminated outdoors, and then bring germs indoors where they dwell on the floors and surfaces.
He said: 'The exposure makes the poison. So if you're not exposed to it, you're not going to get sick from it.'
The only possible cause of this happening would be if the bacteria were lifted into the air we breathe, such as by a draft from a window.
Not only are youngsters playing on the floor at risk - but people who have lower immune systems.
'In a person who is at risk for infections — usually someone recently hospitalized — attention to good household cleaning can be important,' Professor Kevin Garey from the University of Houston College of Pharmacy told Live Science.
Considering we are constantly surrounded by bacteria, those found on the soles of our shoes do not pose an immediate risk - especially in such small amounts.
However, if you have a small child, or are more prone to infection, 'it would be a good idea to take your outdoor shoes off when you enter your home,' Dr Garey said.
'For most healthy persons, however, you can make the decision as much based on preference and habit, as potential health concern.'
A 2008 discovered that the average shoe contains 421,000 units of bacteria on the outside and 2,887 on the interior.
Almost every shoe studied (96 per cent) by the team, led by Dr Charles Gerba, a microbiologist and professor at the University of Arizona, was found to be coated with feacal bacteria called coliforms.
A bacteria called Escherichia coli (E.coli) - a subgroup of coliform - was also present on some shoes.
E.coli could lead to severe diarrhoea, urinary tract infections and even meningitis.
'Not necessarily on every shoe, but on a good majority, you can find some type of E.coli there,' said Dr Sexton.
This article has been adapted from its original source.
