Can syphilis be transmitted through oral sex?

From the Guidelines

Yes, syphilis can be transmitted through oral sex, and the risk of transmission can be reduced by using barrier methods and postexposure prophylaxis with doxycycline, as recommended by the CDC in 2024 1.

Key Points to Consider

• The bacterium Treponema pallidum, which causes syphilis, can enter the body through small breaks in the skin or mucous membranes during oral-genital contact.
• Transmission can occur from performing oral sex on someone with syphilis sores on their genitals or from receiving oral sex from someone with syphilis sores in their mouth.
• Syphilis is particularly contagious during the primary and secondary stages when visible sores (chancres) or rashes are present.
• Using barrier methods like condoms or dental dams during oral sex is recommended to prevent transmission.
• If you suspect exposure, testing is essential as syphilis can be effectively treated with antibiotics, typically penicillin G benzathine (2.4 million units given as an intramuscular injection).
• For those with penicillin allergies, alternatives include doxycycline (100 mg orally twice daily for 14 days) or tetracycline.
• The CDC recommends doxycycline postexposure prophylaxis (doxy PEP) for a selected population, including men who have sex with men (MSM) and transgender women (TGW) who have had a bacterial STI diagnosed in the past 12 months 1.

Prevention and Treatment

• Doxy PEP can be used as postexposure prophylaxis to prevent syphilis and other bacterial STIs, with a recommended dose of 200 mg taken within 72 hours after sex.
• Persons who are prescribed doxy PEP should undergo bacterial STI testing at anatomic sites of exposure at baseline and every 3–6 months thereafter.
• Ongoing need for doxy PEP should be assessed every 3–6 months, and HIV screening should be performed for HIV-negative MSM and TGW according to current recommendations 1.

From the Research

Syphilis Transmission

• Syphilis is a sexually transmitted disease caused by Treponema pallidum, and it can be transmitted through various forms of sexual contact, including oral sex 2.
• The practice of unprotected oral sex may result in infection and development of syphilis, as the bacteria can enter the body through mucous membranes in the mouth 2, 3.
• Oral lesions can be a manifestation of syphilis, and healthcare professionals should be aware of these symptoms to provide accurate diagnosis and treatment 2.

Oral Sex and Syphilis

• Oral sex can lead to the transmission of syphilis, as the bacteria can be present in the mouth and throat of an infected person 3.
• Syphilis can cause lesions in the oral cavity, including on the lips, tongue, and hard palate, which can be a sign of infection 2.
• Asymptomatic oral infections can also occur, making it important to practice safe sex and get regular STI testing 3.

Prevention and Treatment

• Preventive therapy is an important element of syphilis control efforts, and single-dose alternatives to penicillin G benzathine are being studied for treatment of incubating syphilis 4.
• Doxycycline is a recommended second-line treatment for early syphilis, and studies have shown it to be effective in treating the disease 5, 6.
• Systemic treatment of oral STIs usually is the same as that for anogenital infections, and may be accompanied by symptomatic topical therapy 3.