Speaking to USA Today, Dr Jeffrey Kaplan, a biologist from American University in Washington D.C., said fake nails provide ample room for "micro-organisms to adhere to".
"Studies have found 32 different bacteria and 28 different fungi underneath fingernails," he said.
But the extra space of fake nails poses the risk of hiding extra bacteria and fungi.
"There are always bacteria under the fingernail, and you can't get rid of it,' Kaplan said.
"You can transmit fingernail bacteria to your system by scratching, nail-biting, nose-picking and finger-sucking."
According to Kaplan, one study found MRSA — an antibiotic-resistant bacteria that causes serious infections in hospitalised patients — underneath half of the fingernails collected.
Kaplan said that while the fungi and bacteria would most likely not be life-threatening, he warned they could leave your fingernails disfigured.
Healthcare workers require short nails to reduce the risk of transmitting disease, Kaplan added.
The New York Times reported that two nurses may have caused the deaths of 16 babies in 1997 and 1998 at an Oklahoma City hospital.
"When surgeons scrub for surgery, and then they test their hands, there's always bacteria under the fingernail and you can't get rid of it," Kaplan said.