Germs hidden in a kiss

Mouth-to-mouth contact is seen in fish, birds and primates, but intimate kissing involving tongue-to-tongue contact and saliva exchange appears to be unique to humans and is common in more than 90% of cultures. Because?

Some authors suggest that intimate kissing can help you evaluate and emotionally select a future partner based on the chemical sensations produced by saliva.

Others believe that intimate kissing evolved to protect pregnant women from dangerous uterine infections caused by viruses transmitted through saliva: exposure to the virus before pregnancy can immunize the mother and protect the fetus.

In an intimate kiss we exchange 80 million bacteria

In fact, these are just hypotheses and we don’t know the reason why people kiss. Whether it’s mate choice or maternal immunization, there is no doubt that the microbes that live in the mouth are numerous and play an important role.

In a study published in 2014, they analyzed the microbes present in the mouths of 21 couples after an experimentally controlled intimate kiss. They found that when couples kiss, they exchange part of their tongue microbiota, and the other person’s bacteria survive for hours in the saliva of their new resident.

They also noticed that the more we kiss our partner, the more similar the composition of microbes in the saliva between us will be. This seems obvious, but it had to be proven. They even calculated exactly how many kisses were needed to maintain the effect on the salivary microbiota: at least nine kisses per day.

Although the most interesting thing is that the authors of the study calculated the number of bacteria that we exchange during a kiss. To do this, they prepared yogurt with pre-labeled lactobacilli and bifidobacteria and gave it to one of the couples to drink. After a passionate kiss that lasted only ten seconds, they took samples from the “recipient” and counted the number of yoghurt bacteria transferred from one to the other. The conclusion was that in an intimate kiss lasting just ten seconds, we are capable of exchanging approximately 80 million bacteria. With a kiss we exchange not only all our love, but also something as intimate as several million bacteria.

Oral microbiome

The oral microbiome is the community of microorganisms that inhabit the oral cavity (mouth, tongue, gums and throat). It includes thousands of different species of bacteria, viruses, fungi and other single-celled organisms that form a complex and dynamic ecosystem.

More than 700 different species of bacteria have been identified. Most have beneficial effects, such as digesting certain nutrients, protecting against invading pathogens, or regulating the local immune system. Only a few of them are responsible for oral diseases – dental caries, periodontal disease, bad breath, oral candidiasis, etc. – and non-oral diseases – cardiovascular, diabetes and respiratory diseases. Presence of certain oral pathogens such as bacteria. Porphyromonas gingivalis which causes chronic periodontitis, as a risk factor for the formation of amyloid plaques, cognitive impairment and dementia typical of Alzheimer’s disease.

Kissing can transmit herpes

Microorganisms exchanged during a kiss are not necessarily harmful. In most cases, this exchange does not pose a significant health risk as long as people have good general and oral health. But there are several infectious diseases that can be transmitted through kissing.

Herpes is a type of virus that is easily transmitted through saliva. For example, infectious mononucleosis (known as the kissing disease) is caused by the Epstein-Barr virus and is a very common disease among teenagers and young adults. Symptoms include fever, sore throat, extreme fatigue and swollen lymph nodes.

Herpes is transmitted through direct contact, including kissing. Symptoms include painful blisters around the lips or in the mouth. Genital herpes, although most often transmitted through sexual contact, can also be transmitted through kissing if there are active lesions in the mouth or around the lips.

Cytomegalovirus is another herpes that can be transmitted through saliva. Although it does not cause serious symptoms in most cases, it can be dangerous for people with weakened immune systems or pregnant women as it can cause very serious complications during pregnancy.

This mode of transmission explains why the number of people who have antibodies against this type of herpes (prevalence) is so high: for example, more than 70% of the population has been exposed to the Epstein-Barr virus over the years. life.

Caries, pharyngitis and flu

However, there are many more pathogens that can be transmitted through kissing and the exchange of saliva. Among them are some bacteria such as Streptococcus mutans or Streptococcus pyogeneswhich cause tooth decay or throat infections and pharyngitis. But also bacteria associated with periodontal diseases, such as Porphyromonas gingivalis. And, of course, viruses that cause respiratory infections, such as influenza, respiratory syncytial virus, or other cold viruses.

We can also transmit some types of papillomavirus through kissing. And even fungi such as yeast fungal microorganisms albicans what causes candidiasis.

Oral Hygiene for Healthy Kissing

Diet, oral hygiene, smoking and alcohol consumption, use of antibiotics and other medications, genetics and other underlying medical conditions influence the composition and health of the oral microbiota.

Maintaining a healthy balance of oral microbiota is important to prevent diseases and their transmission through kissing. This involves frequent and adequate brushing of the teeth and tongue, combined with the use of dental floss and mouthwash, the latter in moderation. Additionally, regular dental visits, limiting excessive sugar intake and quitting smoking are the best ways to maintain oral health.

And if we’re healthy, we don’t have to worry about sharing our germs.

Ignacio Lopez-Goni, MEMBER of SEM (Spanish Society of Microbiology) and Professor of Microbiology, University of Navarra

This article was originally published on The Conversation. Read the original.

Read more