STI transmission through French kissing: Is it possible?

French kissing, also known as deep kissing, is an intimate expression of affection and passion. It often involves the exchange of saliva, which under certain circumstances can facilitate the transmission of some diseases. But how high is the risk of contracting a sexually transmitted infection (STI) through this form of contact? In fact, some STIs can be transmitted through French kissing – although the risk is generally considered low in most cases. This blog explains which STIs can be transmitted through kissing, how high the actual risk of infection is, and what protective measures you can take to stay safe.

Table of Contents

• Can STIs be transmitted through French kissing?
• Which STIs can be transmitted through French kissing?
• STIs that are very unlikely to be transmitted
• Factors that increase the risk of transmission
• How can I prevent STI transmission through kissing?
• Summary

Can STIs be transmitted through French kissing?

Yes, sexually transmitted infections (STIs) can be transmitted under certain conditions through French kissing. Although the risk is significantly lower compared to other transmission routes, such as unprotected sex, it cannot be completely ruled out – especially during intense and frequent kissing. Factors that influence the likelihood of transmission include the type of infection, the condition of the oral mucosa (e.g., small injuries or inflammation), and the amount of pathogens present in the saliva (Cleveland Clinic, 2024).

Which STIs can be transmitted through French kissing?

Some sexually transmitted infections (STIs) can be transmitted through French kissing under specific conditions. The most relevant infections include:

Herpes Simplex Virus (HSV)
Herpes is one of the most common viral infections. HSV-1, which causes cold sores, is easily transmitted through direct contact with blisters or infected saliva. Infection can occur during kissing even in the absence of symptoms, but kissing with active sores significantly increases the risk. HSV-2, which more commonly affects the genital area, can rarely affect the mouth, especially through oral-genital contact (WHO, 2024).

Syphilis
Syphilis is a bacterial infection that can be transmitted through visible or hidden lesions (sores), such as direct contact with open lesions in the mouth or on the lips. Kissing someone with an active syphilis sore or a cut in or around the mouth increases the risk of transmission. There is a particular risk if syphilitic sores in the mouth go unnoticed and come into direct contact with mucous membranes or saliva during kissing (NHS, 2024).

Human Papillomavirus (HPV)
HPV is a common viral infection transmitted through skin and mucosal contact. Around 40 types of this virus can cause oral HPV infections, nine of which can potentially lead to throat cancer (oropharyngeal carcinoma). The risk of transmission increases if there are injuries or microtears in the oral mucosa. Most people with oral HPV infections show no symptoms, but some may develop sores or lesions on the lips, in the mouth, or throat. HPV vaccination is an essential preventive measure (Ucfs Health, 2023).

Gonorrhoea
Gonorrhoea, caused by the bacterium Neisseria gonorrhoeae, is a sexually transmitted infection that can also affect the throat (oral gonorrhoea). For a long time, transmission through kissing was considered unlikely, but recent studies have shown that gonorrhoea can indeed be transmitted via saliva exchange, particularly when a throat infection is already present. The risk increases with intense or frequent French kissing, especially when combined with other risk factors such as open sores or a high bacterial load (Charleson et al., 2023; Cleveland Clinic, 2024).

STIs that are very unlikely to be transmitted

Some sexually transmitted infections pose an extremely low risk of being transmitted through intimate kissing. These include:

• HIV: HIV is not transmitted through saliva or kissing, as the viral load in saliva is extremely low. Transmission is only conceivable in cases of significant blood contact, such as open wounds in the mouth.
• Chlamydia: Chlamydia, often asymptomatic, primarily affects the genitals, urinary tract, eyes, and occasionally the throat. However, there is no evidence that chlamydia can be transmitted through saliva or kissing.
• Trichomoniasis: The pathogen Trichomonas vaginalis is not transmitted through saliva or French kissing.
  Source: Cleveland Clinic, 2024

Factors that increase the risk of transmission

The risk of transmitting sexually transmitted infections (STIs) through French kissing depends on various factors that can increase the likelihood of infection. The most important factors include:

• Injuries and inflammation: Small cuts, open wounds, or inflammation in the oral mucosa (e.g., due to periodontitis), as well as dental infections or micro-injuries from piercings, provide entry points for pathogens like herpes viruses or syphilis bacteria during intimate kissing.
• Dry mouth: Reduced saliva production weakens the protective function of the mucous membranes, making it easier for pathogens to spread through saliva or mucosal contact.
• High pathogen load: If a person has a high viral or bacterial load in their saliva (e.g., during active herpes, syphilis, or gonorrhoea infections), the likelihood of transmission through kissing increases.
• Kissing behavior: Intense, prolonged kissing or frequently changing partners increases the chances of mucosal contact with infectious saliva or hidden lesions.
• Weakened immune system: People with weakened immune systems are less able to fight off pathogens that may be transmitted through kissing.
• Visible signs of infection: Obvious symptoms like herpes blisters, syphilitic sores, or inflamed areas in the mouth increase the likelihood of pathogen transmission through direct contact.
  Source: CDC, 2024

How can I prevent STI transmission through kissing?

The risk of contracting an STI through intimate kissing can be effectively reduced by the following measures:

• Good oral hygiene: Regular tooth brushing and gum care reduce the risk of injuries and inflammation that could serve as entry points for pathogens.
• Avoid kissing when symptoms are present: Refrain from French kissing if you or your partner have visible signs of infection such as cold sores, ulcers, or inflammation in the mouth.
• Regular STI testing: STI tests help detect infections early and prevent unintended transmission. This is especially important because many STIs are asymptomatic, meaning people may not show symptoms but can still pass on the infection.
• Education: Learn about symptoms and risks to act quickly in case of suspicion. Homed-IQ offers a wide range of blogs on sexual health to help you stay well informed.
• Open communication with sexual partners: Honest and open communication with sexual partners is essential to minimize the risk of STI transmission. Talk about past test results, current health status, and use of protection.

Want to get tested?

In Germany, STI testing is available at local health departments, with general practitioners, or through at-home test kits. Homed-IQ offers 100% discreet at-home STI tests that provide a simple, private, and secure way to get tested. All results are analysed in ISO-certified laboratories also used by clinics and medical practices.

Summary

French kissing is an expression of affection but can, under certain circumstances, lead to the transmission of sexually transmitted infections (STIs). The risk depends on several factors, such as injuries in the oral mucosa, a high pathogen load in saliva, or visible signs of infection. Some STIs like herpes, syphilis, and HPV can be transmitted through French kissing, while the risk for HIV, chlamydia, and trichomoniasis is nearly negligible. Regular STI testing, good oral hygiene, vaccinations, and open communication with sexual partners are key preventive measures.