Although the risk of getting a sexually transmitted infection (STI, which is often used instead of sexually transmitted disease, STD) through kissing is relatively low, it still exists. Herpes, cytomegalovirus (CMV), human papillomavirus (HPV), and syphilis may be transmitted through active lesions (such as cold sores) or saliva. However, kissing will not transmit sexually transmitted diseases like chlamydia, hepatitis, human immunodeficiency virus (HIV), or trichomoniasis. Let's take a closer look at the sexually transmitted diseases that may be transmitted through kissing, as well as their symptoms and treatment methods.

Two similar viruses - herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) - can cause herpes. People may get infected through skin contact, such as during anal sex, oral sex, vaginal sex, or kissing. Most people are infected with HSV-1 before the age of 20.

HSV-1 usually causes cold sores or fever blisters on the gums, lips, mouth, or throat, also known as oral herpes. Cold sores may be red or yellow and form scabs. They may break open and ooze clear or yellow fluid. Multiple small cold sores may also merge into a larger one.

Other symptoms of oral herpes include a burning, itching, or tingling sensation near the lips or mouth, fever, pain when swallowing, sore throat, and swollen glands.

Dr. Graves mentioned that HSV-2 usually causes genital herpes, but if oral sex is involved, it may also lead to cold sores around or inside the mouth. Then, HSV-2 can be transmitted through mouth-to-mouth contact.

CMV is a herpes virus that can be transmitted through saliva during kissing. Approximately 50% to 80% of Americans are infected with CMV before the age of 40. Many infected people are unaware of their infection because CMV usually doesn't cause any symptoms. However, it sometimes causes flu-like symptoms, such as fatigue, fever, loss of appetite, malaise, muscle aches, rash, sore throat, and swollen glands.

There are more than 200 types of HPV, and some of them can be transmitted through deep tongue kissing and oral sex. Oral HPV usually doesn't cause any symptoms, so many people don't know that they are infected. This also makes it easy for oral HPV to spread from person to person. Moreover, HPV may cause oral cancer in some people.

Syphilis is transmitted through direct contact with sores, which usually appear on or around the anus, lips, mouth, penis, rectum, or vagina. Symptoms of syphilis may include rash, fever, hard, round, painless ulcers at the infected site, and swollen lymph nodes. However, the risk of getting syphilis through kissing is relatively low.

Gonorrhea is a common sexually transmitted infection among adolescents. It is usually transmitted through unprotected anal sex, oral sex, or vaginal sex and may be transmitted from mother to fetus during pregnancy. You may also get infected with gonorrhea if your eyes come into contact with the infected fluid. Research has found that oral gonorrhea may be transmitted through kissing. However, oral gonorrhea usually doesn't cause any symptoms, and most cases will disappear within seven days.

Some sexually transmitted diseases will not be transmitted through daily contact like kissing.

This is a common sexually transmitted infection caused by the bacterium Chlamydia trachomatis. It may be transmitted through unprotected anal sex, oral sex, or vaginal sex. Pre-ejaculatory fluid, semen, and vaginal fluid may carry Chlamydia trachomatis. If you touch your eyes with the infected fluid, you may also get infected. Moreover, chlamydia may be transmitted from mother to fetus during pregnancy.

Hepatitis causes inflammation of the liver. There are several types, such as hepatitis B and hepatitis D, which can be transmitted through unprotected sexual contact. However, hepatitis B virus is not carried in saliva, so it will not be transmitted through kissing. Hepatitis D will not be transmitted through kissing either.

HIV may be transmitted through blood, breast milk, rectal fluid, pre-ejaculatory fluid, semen, and vaginal fluid. Unprotected anal sex or vaginal sex or sharing drug injection equipment may lead to HIV infection. HIV will not be transmitted through saliva, sweat, or urine. Only when both parties have bleeding gums or ulcers may HIV be transmitted through kissing.

Pre-ejaculatory fluid, semen, and vaginal secretions may carry the parasite that causes trichomoniasis (also known as "trich"). Trichomoniasis is usually transmitted through unprotected vaginal sex and vulvar contact. Touching your eyes or using sex toys with infected fluid may also lead to infection.

The treatment methods vary depending on the cause of the oral sexually transmitted infection.

For example, cold sores caused by oral herpes usually disappear on their own within one to several weeks. Some home treatment methods may help relieve symptoms, such as applying ice cubes or warm towels to the affected area to relieve pain, washing cold sores with antibacterial soap and water, eating fruit-flavored popsicles, rinsing the mouth with cold water or flushing with saline solution, avoiding citrus fruits, hot drinks, salty and spicy foods, and using Tylenol (acetaminophen) to relieve pain. Antiviral drugs such as acyclovir, famciclovir, and valacyclovir can also be taken to reduce the frequency of cold sore outbreaks. However, oral herpes is a chronic infection, and antiviral drugs cannot cure it. People who often have cold sores may need to take antiviral drugs continuously.

Like oral herpes, CMV and oral HPV usually can recover without medication. Painkillers can be taken or the mouth can be rinsed with saline solution to help treat CMV. People with weakened immune systems may need antibody therapy or antiviral drugs.

Syphilis can be treated with penicillin, an antibiotic. For those who are allergic to penicillin, doxycycline can be taken instead.

Preventing oral sexually transmitted infections can be difficult. After all, people are unlikely to ask about each other's complete sexual history before the first kiss. However, healthcare providers suggest several ways to reduce the risk. You can ask relevant questions first. Although kissing usually happens spontaneously and it may be a bit embarrassing to talk about sexual health issues before kissing, Dr. Graves pointed out that it is completely acceptable to do so. Try not to kiss people with cold sores, because if the other person doesn't have herpes, the possibility of getting herpes or syphilis will be lower than that of those with active lesions. In addition, practicing monogamy can also reduce the risk. Dr. Graves said that being monogamous with a partner who doesn't have sexually transmitted diseases means you won't be exposed to such diseases.

Compared with anal sex, oral sex, and vaginal sex, kissing is a low-risk behavior. However, sexually transmitted infections like herpes, HMV, HPV, and syphilis may still be transmitted through active lesions or saliva. Most oral sexually transmitted infections will disappear on their own. Taking painkillers and rinsing the mouth with saline solution may help treat oral herpes and CMV. Some people may need to use antibiotics or antiviral drugs to treat oral sexually transmitted infections. If you notice symptoms of oral sexually transmitted infections or have recently been exposed to sexually transmitted infections, you should consult a healthcare provider.

Some sexually transmitted infections, such as CMV or oral HPV, usually don't have any signs or symptoms. However, in other cases, signs and symptoms of oral sexually transmitted infections (such as herpes and syphilis) may be noticed, such as body aches, chancres (painless red sores in syphilis patients) on the tongue or throat, fever, headache, joint pain, lesions similar to fever blisters (in the case of herpes), sore throat, and swollen glands. It should be noted that blisters or chancres may disappear, but this doesn't mean that you no longer have herpes or syphilis. There may be "outbreaks", that is, the signs and symptoms may reappear.

Whether or not you swallow semen, unprotected oral sex will increase the risk of certain sexually transmitted infections, such as chlamydia infection, gonorrhea, hepatitis, herpes, and HPV. Even if there is no ejaculation, certain sexually transmitted diseases (such as chlamydia or gonorrhea) may still be transmitted because other body fluids (such as pre-ejaculatory fluid) carry infectious particles. Active lesions around or on the genitals, such as herpes or HPV, may also transmit sexually transmitted infections without ejaculation. Moreover, spitting out semen during oral sex cannot protect you from sexually transmitted infections. Instead, using condoms or dental dams can reduce the risk.