The answer to whether you can get sick is a definite yes, because mouth-to-mouth contact facilitates the transfer of viruses and bacteria carried in saliva and respiratory droplets. While the risk of contracting a serious illness from a casual kiss is generally low, the mechanism allows for the spread of numerous common and specific pathogens. This article will focus on the diseases most commonly passed through this intimate form of contact and the circumstances that increase the likelihood of transmission.
The Mononucleosis Connection
The illness most famously linked to this activity is infectious mononucleosis, commonly known as “The Kissing Disease.” This infection is overwhelmingly caused by the Epstein-Barr Virus (EBV). EBV spreads very efficiently through saliva, which is why close contact like kissing is a common transmission method.
Symptoms of mononucleosis typically appear four to six weeks after exposure and often include extreme fatigue, a high fever, and swollen lymph nodes in the neck and armpits. The virus can remain in a person’s saliva and be shed for many months, even after the acute symptoms have disappeared. This long shedding period means that an infected person can unknowingly pass the virus to others, making prevention challenging.
Viruses and Bacteria Spread Through Saliva
Beyond mononucleosis, many illnesses can be spread through the close contact of kissing. The exchange of saliva and the expulsion of respiratory droplets during a kiss provide a direct path for various viral and bacterial pathogens to enter a new host. Colds and influenza are easily transmitted this way because the infectious particles are present in the nose and throat secretions that mix with saliva.
Infections like Group A Streptococcus, the bacteria responsible for Strep Throat, can also be transmitted via saliva exchange. While most deep kisses exchange hundreds of different types of bacteria, the transfer of a specific pathogenic strain like Streptococcus can lead to illness. Similarly, viruses like coronaviruses, including the one that causes COVID-19, are known to spread through the small, aerosolized droplets expelled during close contact.
The risk is highest when the infected person is actively symptomatic, but transmission can occur even during the pre-symptomatic phase when the viral or bacterial load is building. Cytomegalovirus (CMV), another common herpesvirus, is also known to be spread through saliva.
When Open Sores Introduce Risk
Active lesions or open sores are present in or around the mouth. This is particularly relevant to the Herpes Simplex Virus 1 (HSV-1), which is the primary cause of oral herpes, commonly known as cold sores. HSV-1 is most contagious when a blister is visible and actively shedding fluid, as the viral concentration in the lesion is extremely high.
Transmission occurs through direct contact with the sore itself or the fluid it contains, though the virus can also be shed in saliva even without visible symptoms. Other pathogens that may be present in a sore can also be transmitted this way, including the bacteria that cause Syphilis, though this is a less common route than through other sexual contact. The presence of any break in the skin or mucosal surface, such as a canker sore or a bleeding gum line, can increase the risk for various infectious agents to be passed.
Practical Steps for Risk Reduction
The first step is to avoid kissing when either person is feeling unwell. This means refraining from close contact at the first sign of a cold, fever, sore throat, or general fatigue. Since the presence of active cold sores dramatically increases the risk of HSV-1 transmission, it is prudent to completely avoid kissing until the lesion has fully healed.
Maintaining good oral hygiene, including regular brushing and flossing, helps to reduce the overall load of bacteria and viruses in the mouth. If you are aware that a partner is actively ill or has a visible lesion, it is safer to opt for a hug or a kiss on the cheek to prevent the direct exchange of saliva and infectious droplets.