10/21/2012 11:57 EDT | Updated 12/22/2012 05:12 EST

Read my Lips: Kissing is a Germy Affair

2012-05-28-GermGuyBanner.jpg The mouth is full of germs and all one needs to do is lick a petri dish -- or convince someone else to do so -- to see the amount and variety of microbes that lurk inside the oral cavity. By kissing another person, especially passionately, the transfer of germs is not just likely, it's inevitable...

closeup of a couple kissing

Earlier this year, a new advertising campaign emerged encouraging consumers hoping to seal the deal with a partner to "Practice Safe Breath." The premise was pure genius: unabashedly taking from the ubiquitous public service messages for safe sex and creating a new, amusing message. The point was obviously to sell more products and yet from a hygiene perspective, the concept seems pretty sound.

The mouth is full of germs and all one needs to do is lick a petri dish -- or convince someone else to do so -- to see the amount and variety of microbes that lurk inside the oral cavity. By kissing another person, especially passionately, the transfer of germs is not just likely, it's inevitable. There are millions of bacteria in each millilitre of saliva and as many as 10,000 different types just waiting to spread.

The majority of these oral occupiers, better known as the mouth microflora, are harmless although there are several pathogens that can make a person sick. Some are obvious to spot thanks to symptoms such as the unattractive inflammation and congestion of a cold or flu infection or the aesthetically frustrating cold sore, which indicates a herpes simplex virus infection. But a host of others are not so easily spotted yet can cause some rather severe health complications.

Several bloodborne infections can potentially spread through kissing, such as HIV but the circumstances required -- including bleeding gums and/or cuts inside the mouth -- make any transfer highly unlikely. The same can be said about the potentially deadly meningitis bacteria, which is part of the normal mouth microflora in about 20 per cent of individuals.

The risk for spread and infection increases with the number of kissing partners taking the concept of relationship roulette to a completely different level. Thankfully for gamblers of love, there is a vaccine against meningococcal bacteria to help keep the risk of a poor partnering limited to emotional pain.

The most well-known of all the lip-locking infections is mononucleosis, the kissing disease. The infection is caused by the Epstein-Barr Virus and can be found in high numbers in the saliva of sufferers. As anyone who has had mono knows, the symptoms are sore throat, a slight fever, swollen lymph nodes and a fatigue that lasts for weeks to months. Worse, there is no cure for the disease; one must wait it out and ensure that they refrain from kissing during that time.

With all these possibilities for a rather unkind outcome to a pleasurable moment, one might believe that kissing should be avoided outright and even placed as a risk factor for the acquisition of infectious diseases. As history has revealed, however, kissing may have been adopted by humans for that same reason. After all, sharing germs via this route with a prospective partner is a relatively safe way to ensure a valid match exists not only in technique but also in biology.

The immune system is the body's defense against infectious disease and reacts to anything foreign coming into the body. Trying new foods may cause stomach aches and gastrointestinal problems while breathing in foreign air may lead to constriction of the air pathways. In the same way, when the foreign entities of another person's saliva -- or tongue -- enters the oral cavity, the immune system immediately responds to the introduction and initiates what is known as an oral immune response. Anything not considered to be friendly will be attacked, leading to a localized battle inside the mouth and a feeling of uneasiness throughout the rest of the body; a natural form of morning remorse.

If however, the immune system sees friendly components, including harmless microflora species as well as salivary proteins, sugars and genetic material, the immune system will do a quick check but not invoke a response. Even if there is a foreign entity that is tolerable, such as the cytomegalovirus, which is harmless to adults but can maim and kill an unborn child, the response will be minimal and the person will feel fine whilst sharing.

A good match will offer a sense of calm, enjoyment, and the production of wonderful hormones that lead to visions of a successful future mating, at least at the biological level. Moreover, by keeping the cytomegalovirus at bay, any future pregnancies may be less problematic.

While kissing may offer insight into the long term future of a relationship, there is little doubt that the act is also transient and may lead to a much shorter duration of mating. There may be no care for the future and more importantly of the germs that might be shared. But a quantum of sedulousness is required when thinking about being overly promiscuous in kissing. After all, each kiss may feel like a bond but could end up costing at least one person more than a few moments of unease.

As for the idea of practicing safe breath to reduce the risk of sharing germs, another option may be necessary. In 2007, a scientific study focusing on chewing gums containing breath freshening ingredients revealed these products do little to reduce the number of microbes in the mouth.

The only effective way to prevent sharing is through suppression and the use of an alternate means of affection, like a hug or a kiss on the cheek. Granted, they are not the most pleasurable choices but in times of suspicion -- or bad dates -- they are a great way to stay safe.

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