It is no secret that kissing means sharing germs.  However, a new study published in the journal Microbiome reveals just how many germs are swapped.  In an intimate kiss, roughly 80 million bacteria are transferred in about 10 seconds.  Also, couples that have a higher frequency of intimate kissing had a similar profile of salivary microbiota.

According to EurekAlert, there is an ecosystem of more than 100 trillion microorganisms that live in the human body.  This salivary exchange of 80 million is just a small portion of that.  Also, bacteria are not necessary “gross” or bad.  They are essential for food, synthesizing nutrients, and preventing disease.  In addition to kissing, the variation in bacteria is shaped by genetics, diet, and age.

A study published earlier this year in the journal Nature explains that microbes in the gut are associated with susceptibility to pathogen infection.  This means that, depending on the bacterial profile in the digestive system, some individuals may be more likely to contract some infections than others.  The Wall Street Journal reports that another study from earlier this month showed how gut bacteria can also impact weight gain (or reduced vulnerability to weight gain).

However, these studies should all be received with caution.  According to BMC Biology, studies of microorganisms are often contaminated, drawing the results into question.  The contaminating varieties of bacteria are those that are often found in different chemical reagents and naturally occurring in soil and water and on human skin.  Given that these contaminants may be present in studies, the results may be tainted or skewed by the presence of additional bacteria not from the area studied.