Most sexually transmitted diseases (STDs) transmit through genital fluids or sexual contact. However, a few STDs can spread through kissing or other contact with oral fluids or sores.

Below, we look into which STDs are transmissible by kissing, which are not, and other diseases that can spread in this way.

A couple kisses and it is possible you can get an std from kissing.Share on Pinterest
There are more than 26 known STIs, and kissing can spread four of them.

Many STDs either cause no signs or symptoms or they cause symptoms so mild that they are easy to overlook. Still, it is important to treat the underlying infection.

Since not all of these health issues cause obvious problems, sexually transmitted infections (STIs) may be a more accurate term than STDs, the American Sexual Health Association note.

There are more than 26 infections that mainly spread through sexual contact. A vast majority of STIs are transmitted through contact with the genitals, including genital fluids or sores, typically during intercourse or oral sex.

For most healthy people, kissing is a very low risk sexual activity.

But a few STIs can spread through kissing, especially when someone has an active infection or symptoms such as oral sores. Among these infections are:

Herpes

The herpes simplex virus has two subtypes: HSV-1 and HSV-2.

Both viruses cause lifelong infections. A person with either infection can experience symptom-free periods followed by symptoms.

Herpes is most contagious when symptoms are present, but a person can still pass it on when they are asymptomatic.

Most people with oral herpes have an HSV-1 infection. This causes sores, painful blisters, or ulcers to form in, on, or around the mouth or lips. These skin lesions are often known as cold sores.

In most cases, HSV-1 spreads through oral-to-oral contact such as kissing.

The World Health Organization (WHO) report that roughly 3.7 billion people under the age of 50 have HSV-1 infections around the world. Most people acquire it in childhood.

Meanwhile, an estimated 491 million people aged 15–49 worldwide have an HSV-2 infection. This typically causes painful genital sores, blisters, or ulcers. It spreads through sexual contact, usually genital-to-genital contact.

People with HSV-1 may not require professional treatment. It is important to practice good hygiene, and a person may use over-the-counter medication to combat cold sores. People with active sores may want to avoid kissing until their sores go away.

People with HSV-2 may take antiviral medications indefinitely to reduce the risk of experiencing symptoms and transmitting the virus.

Syphilis

Syphilis is a bacterial STI spread through direct contact with a syphilis sore. These sores can develop on the genitals, in the mouth, or on the lips. Syphilis can also spread to a baby during pregnancy.

Symptoms grow more severe as syphilis progresses. Initially, a person tends to have round, firm, painless sores. These often heal on their own within 3–6 weeks.

Later, a person may develop a rough, reddish-brown rash, which may appear on the palms of the hands, the soles of the feet, or both. A person may not notice the rash right away, as it may not itch.

A person with syphilis may also experience:

These symptoms often resolve on their own. However, anyone with syphilis requires antibiotic treatment to prevent the disease from progressing.

Within 10–30 years of the initial infection, syphilis can cause life-threatening complications. At this stage, a doctor may refer to the issue as tertiary syphilis.

Some people have latent syphilis — they experience no symptoms early on. However, if they do not receive treatment, they can develop the dangerous health issues associated with tertiary syphilis and require urgent medical care.

Cytomegalovirus

Cytomegalovirus (CMV) is very common — nearly 1 in 3 children in the United States develop the infection by age 5, and more than half of the adults in the country have it by age 40.

The virus can spread through direct contact with bodily fluids, including semen, breast milk, blood, and tears. It also spreads through contact with saliva or urine — especially in babies and younger children.

In healthy people, the immune system usually prevents CMV from causing severe infection or illness. Most people with the infection are unaware that they have it.

When CMV does lead to symptoms, it tends to cause:

  • a sore throat
  • fatigue
  • a fever
  • swollen lymph nodes

People with compromised immune function and a CMV infection may experience more severe symptoms that affect the lungs, liver, eyes, esophagus, stomach, and intestines.

A baby born with a CMV infection may have impaired growth, hearing loss, and problems affecting the brain, liver, spleen, and lungs.

Once someone has a CMV infection, they have it for life, and it can reactivate.

There is no cure for CMV, but most people who have the infection do not require treatment. Babies and people with reduced immune function may need to take antiviral medications to prevent complications.

HPV

HPV stands for human papillomavirus. There are several of these viruses, and some can cause cancer later in life.

In rare cases, a person can pass the infection through oral contact or contact with infected saliva. The most common way to transmit the virus is through direct contact with the genitals, however.

Around 3.6% of women and 10% of men in the U.S. develop oral HPV. Most people clear the infection within a couple of years.

Oral HPV infects the throat and mouth and can cause cancers of the oropharynx, the back of the throat, the base of the tongue, and the tonsils. Health experts believe that 70% of cases of oropharyngeal cancer in the U.S. are caused by HPV.

Common symptoms of oropharyngeal cancer include:

  • a persistent sore throat
  • hoarseness
  • swollen lymph nodes
  • pain while swallowing
  • unexplained weight loss
  • an earache

A majority of STIs are not transmitted through kissing, including:

A person can acquire and pass on a range of health problems through contact with saliva or oral sores.

Common diseases or pathogens that can be transmitted through kissing include:

There are more than 26 STIs, and only four of these can be passed on through kissing.

It is always a good idea for people to discuss any health issues or concerns before engaging in sexual activities.

To reduce the risk of developing STIs, a person can use barrier protection, such as condoms, during sex, or limit forms of sexual activity.

Anyone who believes that they may have an STI should consult a doctor.