Transmission of a sexually transmitted infection (STI) from receiving oral sex is possible. Oral sex, which involves using the mouth to stimulate a partner’s genitals, carries a risk of STI transmission similar to vaginal or anal sex. The risk depends on the specific infection, the presence of symptoms, and whether barrier methods are used. This risk applies to both the person giving and the person receiving oral sex.
Understanding Transmission Risk
STIs spread primarily through contact with infected bodily fluids or skin-to-skin contact with infectious lesions or sores. Bodily fluids like pre-ejaculate, semen, and vaginal fluids can carry bacteria and viruses from the genitals into the mouth and throat during oral contact. The lining of the mouth and throat contains mucous membranes, which are thinner and more delicate than skin, making them vulnerable entry points for pathogens.
The presence of open cuts, small abrasions, or inflammation in the mouth or on the genitals can significantly increase the chance of transmission. Even micro-tears in the delicate tissues, which may not be visible, can allow bacteria and viruses to enter the bloodstream or local tissues. Brushing teeth or flossing immediately before oral sex can create these small breaks in the gum tissue, raising the risk for the person giving oral sex.
Key Infections Transmitted
Herpes Simplex Virus (HSV)
Herpes is highly transmissible through oral sex, spreading via skin-to-skin contact, even when no symptoms are visible. Receiving oral sex from a partner with oral herpes (often HSV-1) can lead to a genital herpes infection. Conversely, oral contact with a partner who has an active genital herpes lesion (often HSV-2) can cause an oral herpes infection.
Gonorrhea and Chlamydia
Gonorrhea and Chlamydia are common bacterial infections that can thrive in the throat, known as a pharyngeal infection. Receiving oral sex from a partner who has a throat infection can lead to a genital infection. Gonorrhea transmission from an infected throat to the penis is estimated to be between 23% and 42.3% per unprotected encounter.
Syphilis
Syphilis is transmitted through direct contact with a chancre, a firm, painless sore that marks the first stage of the infection. If a partner has a chancre on their lips, mouth, or throat, receiving oral sex presents a risk of transferring the infection to the genitals. The risk of transmitting syphilis through oral sex is estimated to be between 10% and 30% per unprotected encounter.
HIV and Hepatitis B
While the risk of Human Immunodeficiency Virus (HIV) transmission from oral sex is considered very low, it is still possible. Transmission risk is primarily associated with the presence of open sores, bleeding gums, or cuts in the mouth or on the genitals. Hepatitis B (HBV) can also be transmitted through oral sex, particularly if there is contact with infected blood or semen. A vaccine is available to prevent HBV infection.
Symptoms and Diagnosis
Many oral and pharyngeal STI infections, particularly Gonorrhea and Chlamydia, often present with no noticeable symptoms. When symptoms occur, they can be subtle and may include a persistent sore throat, difficulty swallowing, or a burning sensation in the throat. Syphilis or Herpes may present as painless sores or lesions on the lips, tongue, or inside the mouth.
For accurate diagnosis, standard urine or blood tests designed for genital infections may not be sufficient to detect a throat infection. A healthcare provider will often need to perform a specific throat swab, similar to a throat culture for strep throat, to test for bacterial infections like Gonorrhea and Chlamydia. It is important to inform the healthcare provider about specific sexual activities, including oral sex, to ensure the correct testing is ordered.
Effective Risk Reduction Methods
Using barrier methods is a practical strategy for minimizing the risk of STI transmission during oral sex. For oral sex on the penis, a non-lubricated latex or plastic condom can be used to cover the entire shaft. For oral sex on the vulva or anus, a dental dam—a thin sheet of latex or polyurethane—can be placed as a physical barrier between the mouth and the genital or anal area.
If a dental dam is not readily available, a latex or polyurethane condom can be unrolled and carefully cut into a square sheet for use as a barrier. Avoiding oral sex when either partner has visible sores, cuts, or bleeding gums further reduces the transmission chance. Regular STI screening, especially with specific testing for oral and pharyngeal sites, is necessary for sexually active individuals.