Step away from the makeup tester samples at your local department store because they're mini petri dishes teeming with bacteria, mould and even fecal matter.

According to an article in the Daily Mail, US TV show, Good Morning America, went undercover to test the makeup testers from 10 stores across two American states.

They took swab samples from lipstick, eyeshadow, concealer and other beauty products from a range of different department stores which they then sent off to be analysed at New York University's microbiology department.

The results showed the worst. Most testers were brimming with germs - a result of hundreds of different people trying them out on a daily basis.

One in every five samples displayed significant growth of mould, yeast and bacteria and found that foundation, brushes, eyeliner and eyeshadows had the most bacteria. No difference between upscale and cheaper department stores was found.

The team also found that those beauty samples are only replaced once or twice a year - another reason for a huge germ population.

Makeup experts suggest using the foundation samples on the neck rather than the face and when choosing a lipstick colour to use the top of your hand instead of on your lips.

And when it comes to eyeliner and eyeshadows a disposable applicator, such as a clean earbud, should be used.

"If you have an open cut, you might not want to go the route of using makeup that has been used by other people," suggests Philip Tierno, Director of Microbiology at NYU Langone Medical Centre.

Allure editor-in-chief, Linda Wells, added: "To me, makeup testers are like petri dishes: I would not want to go near one. There are better ways to do it."