STI Risk from Oral Sex: What You Need to Know

Oral sex, including blowjobs, carries a risk of transmitting sexually transmitted infections (STIs) such as chlamydia, gonorrhoea, or herpes. A blowjob refers to the stimulation of the male genitalia by a partner using the mouth, lips, and tongue, and is one of the most common forms of oral sex. This blog provides information about the risks of STI transmission through blowjobs, outlines common STIs, and offers practical tips on how to protect yourself effectively.

Table of contents

• Can you get a sexually transmitted infection from a blowjob?
• Which STIs can be transmitted through a blowjob?
• What are the symptoms of an STI?
• How can I protect myself from an STI during a blowjob?
• Summary

Can you get a sexually transmitted infection from a blowjob?

Yes, blowjobs can transmit sexually transmitted infections (STIs). This happens through direct contact with infected mucous membranes, bodily fluids such as semen or vaginal secretions, as well as through small injuries in the mouth or on the genitals. Both the performing and the receiving partner can become infected. While the risk of transmission through blowjobs is generally lower than with vaginal or anal sex—since contact with mucous membranes and bodily fluids is usually more limited—there is still a risk of infection, which is often underestimated (CDC, 2024).

What does the risk of contracting an STI during a blowjob depend on?

The risk of STI transmission during a blowjob depends on:

• Type of STI: Some sexually transmitted infections, such as gonorrhoea or herpes, are highly contagious and can be transmitted through minimal contact with mucous membranes or small amounts of bodily fluid.
• Presence of injuries: Small cuts or tears in the mouth, on the lips, or genitals significantly increase the risk of transmission, as pathogens can enter the body more easily.
• Protective measures: The use of condoms or dental dams during oral sex significantly reduces the risk of transmission by providing a barrier against direct contact with infected fluids or mucous membranes.
• Viral/bacterial load: A high concentration of pathogens (e.g. in untreated infections) increases the likelihood of transmission.
• General health condition: A weakened immune system, for example due to illness or medication, makes the body more susceptible to infections and increases the risk of contracting an STI.

Source: Cleveland Clinic, 2023

Which STIs can be transmitted through a blowjob?

Several sexually transmitted infections (STIs) can be transmitted during a blowjob, as bodily fluids and mucous membranes come into direct contact. These include:

• Gonorrhoea: This bacterial STI infects the mucous membranes of the throat and genitals. It can be transmitted during a blowjob if infected fluids such as semen or vaginal secretions enter the mouth. Transmission from an infected throat or mouth to the genitals is also possible.
• Chlamydia: Chlamydia often causes symptomless infections and can be transmitted during oral sex through direct contact with infected mucous membranes or bodily fluids.
• Syphilis: This bacterial infection is transmitted through open sores or direct mucous membrane contact. During a blowjob, small injuries in the mouth or on the genitals can serve as entry points for the bacteria. If symptoms occur, syphilis often presents with highly contagious sores.
• Herpes: This virus causes blisters on the lips or genitals and is highly contagious. Oral herpes can easily be transmitted to the genitals, and genital herpes to the mouth, especially through direct contact with open sores.
• HPV (Human papillomavirus): These viruses are transmitted through direct skin-to-skin contact and bodily fluids. In most cases, the infection clears up on its own, but some HPV types can cause warts in the genital or oral area and, in rare cases, lead to mouth and throat cancer.
• HIV: Transmission of the virus during a blowjob is rare but possible if blood is involved—for example, from mouth injuries, bleeding gums, or genital injuries. The risk increases if the partner has a high viral load.

Sources: Cleveland Clinic, 2023, Mayo Clinic, 2024

What are the symptoms of an oral STI?

Many STIs do not only affect the genital area but can also infect the mouth and throat (oral STIs). The following symptoms may indicate an oral STI:

• Sore throat, similar to pharyngitis (e.g. in gonorrhoea or chlamydia)
• Sores or blisters on the lips, oral mucosa, or tongue (herpes, syphilis)
• White or yellowish coatings in the throat (gonorrhoea)
• Pain or swelling of the lymph nodes in the neck
• Warts in the mouth or throat area (HPV)

Important: Many STIs are asymptomatic—both genitally and orally—which means they can occur without visible symptoms but still be transmitted. If left undetected, they may lead to long-term health consequences. That’s why regular testing is essential (Mayo Clinic, 2024).

How can I protect myself from an STI during a blowjob?

The following measures help reduce the risk of contracting an STI through oral sex:

• Use condoms or dental dams: When used correctly, they offer effective protection against pathogens. Make sure the condom fits properly and is undamaged.
• Maintain good oral hygiene: Regular brushing, flossing, and avoiding hard or sharp-edged foods reduce the risk of injuries or inflammation that can serve as entry points for infections.
• Avoid sexual contact if in doubt: If you have symptoms such as blisters, sores, or any other signs of an STI, refrain from sexual contact until you’ve been medically evaluated.
• Get tested: Regular STI testing is important, especially with new or changing partners, as many infections occur without symptoms. Tests can be done at a doctor’s office, health department, or anonymously at counselling centres. Alternatively, home test kits are also available that are discreet and easy to use, such as those from Homed-IQ.

Source: NHS, 2024

Summary

Blowjobs, a common form of oral sex, carry a risk of transmitting sexually transmitted infections (STIs) such as chlamydia, gonorrhoea, herpes, or HPV. Infections can be transmitted through direct contact with mucous membranes, bodily fluids, or small injuries in the mouth or on the genitals, putting both the giving and receiving partner at risk. Many STIs are asymptomatic but can lead to long-term health problems if left undetected. Protective measures—such as the use of condoms or dental dams, along with regular STI testing—are essential to minimise the risk of infection.