Researchers at Aberystwyth University in the UK said habitual handshaking allows movement of germs between people, and can help spread contagious illness.
Using rubber gloves and a thick layer of E coli, scientists exchanged handshakes, high fives and fist bumps.
They found that transfer of potentially disease-causing bacteria is highest during a handshake.
Dr Dave Whitworth, Senior lecturer at Aberystwyth University, and PhD student Sara Mela carried out the research, dipping a glove into a bacterial broth before gingerly extending a hand.
The pair tested three different greetings and assessed the amount of germs transferred from each contact.
They found that a high dose of bugs were passed on during a handshake.
This was reduced by over half in the high-five, and germ transfer was a whopping 90 per cent lower when bumping fists.
The hygienic nature of the fist bump may be due in part to its speed (typically much quicker than a first-rate handshake) but also because there is a smaller area involved.
Direct contact is needed for most microbes to move, so minimising the parts of the hand that touch gives bacteria less chance to spread.
The fist-bumping researchers also looked at grip strength and found that a stronger handshake increased the amount of bacteria shared.
The study was published in the American Journal of Infection Control.