Can You Get an STI From Oral Sex Without Symptoms? What the Science Says

The Perception vs The Reality

Many people believe oral sex is essentially "safe sex" – that without penetration, the risk of STI transmission is negligible. Some assume that if neither partner has visible symptoms, there's nothing to worry about.

The science tells a different story. While oral sex does carry lower risk for some infections compared to vaginal or anal sex, it's far from risk-free – and the absence of symptoms is not a reliable indicator of safety.

Can STIs Really Spread Through Oral Sex?

Yes, absolutely. Several STIs can be transmitted through oral-genital contact, oral-anal contact (rimming), and even oral-oral contact in some cases.

The mouth, throat, and genitals all have mucous membranes that can harbour infections and facilitate transmission. And here's the crucial point: most oral STI infections cause no symptoms at all.

Which STIs Can You Get From Oral Sex?

High Transmission Risk

Herpes (HSV-1 and HSV-2)

• Oral herpes (typically HSV-1) can spread to genitals during oral sex
• Genital herpes (typically HSV-2) can spread to the mouth
• Transmission can occur even without visible sores (asymptomatic viral shedding)
• Up to 70% of new genital herpes cases are caused by HSV-1 transmitted through oral sex

**Gonorrhoea**

• The throat can become infected through giving oral sex to an infected partner
• Oral gonorrhoea is usually completely asymptomatic
• Can then spread to partners' genitals through oral sex
• Increasing antibiotic resistance is a concern

**Syphilis**

• Transmission occurs through contact with syphilis sores (chancres)
• Sores can appear in the mouth, lips, throat, or genitals
• Primary sores are often painless and may go unnoticed
• Early syphilis is highly infectious

HPV (Human Papillomavirus)

• Can infect the mouth and throat through oral sex
• Oral HPV infections are usually asymptomatic
• High-risk oral HPV can cause throat cancers
• Low-risk types can cause oral or genital warts

Moderate Transmission Risk

**Chlamydia**

• Can infect the throat, though less efficiently than gonorrhoea
• Throat chlamydia is usually asymptomatic
• Less commonly diagnosed but can occur

Hepatitis A

• Transmitted through oral-anal contact (rimming)
• Spreads through faecal-oral route
• Vaccination available and recommended for at-risk groups

**Hepatitis B**

• Can be present in saliva, though transmission through kissing alone is rare
• Risk increases with oral sex involving blood or sores
• Vaccination provides excellent protection

Lower Transmission Risk

**HIV**

• Risk of HIV transmission through oral sex is very low but not zero
• Estimated at 0.04% per act for receptive oral sex with ejaculation
• Risk increases with mouth sores, bleeding gums, or presence of other STIs
• Still recommended to avoid ejaculation in mouth and consider PrEP if at higher risk

The Asymptomatic Problem

Here's why the absence of symptoms provides false reassurance:

Most Oral STI Infections Are Silent

• Oral gonorrhoea: 90%+ have no symptoms
• Oral chlamydia: Usually asymptomatic
• Oral HPV: Almost always asymptomatic until complications develop
• Oral herpes: Many people don't recognise mild or atypical outbreaks

Genital Infections Are Often Asymptomatic Too

• **Chlamydia**: 70% of women and 50% of men have no symptoms
• **Gonorrhoea**: 50% of women and 10% of men are asymptomatic
• **Herpes**: Up to 80% of people with genital herpes don't know they have it

Transmission Doesn't Require Symptoms

• Viral shedding can occur without visible sores
• Bacteria can be present in sufficient numbers to transmit without causing symptoms
• You cannot tell by looking whether someone has an STI

The Research Evidence

Studies consistently show that oral sex is an underappreciated transmission route:

[Herpes](/conditions/herpes)

A landmark study found that HSV-1 transmitted through oral sex now causes a majority of new genital herpes cases in young people in developed countries. This shift occurred because oral sex has increased while fewer young people carry HSV-1 from childhood.

Gonorrhoea

Research on men who have sex with men has found that over 80% of pharyngeal (throat) gonorrhoea cases occurred in participants who had no symptoms. The throat acts as a reservoir for the infection.

HPV and Throat Cancer

Studies show that oral HPV infection, acquired through oral sex, is responsible for the rising rates of oropharyngeal (throat) cancer, particularly in men. The risk increases with the number of oral sex partners over a lifetime.

Syphilis

Outbreak investigations have confirmed that oral sex, including oral-oral contact through kissing when sores are present, can transmit syphilis. Primary chancres in the mouth or throat are easily missed.

Who Is Most at Risk?

While anyone who has oral sex has some level of risk, certain factors increase transmission likelihood:

Factors That Increase Risk

• Having multiple oral sex partners
• Not using barrier protection (condoms, dental dams)
• Having cuts, sores, or inflammation in the mouth
• Recent dental work or bleeding gums
• Presence of another STI (increases susceptibility)
• Giving oral sex to someone with a genital infection

Often Overlooked Risk Groups

• People in long-term relationships who had previous partners
• Those who only have oral sex (thinking it's "safe")
• People who wouldn't consider themselves "at risk"

How to Reduce Your Risk

Use Barrier Protection

• Condoms for oral sex on a penis – reduce transmission significantly
• Dental dams for oral sex on a vulva or anus – create a barrier
• Admittedly underused, but effective when used correctly

Get Tested Regularly

• Include throat swabs if you give oral sex (especially for gonorrhoea)
• Standard STI screening may not test the throat unless you ask
• Test between partners and annually if sexually active

Communicate With Partners

• Discuss STI status and testing
• Share information about any symptoms
• Make informed decisions together

Consider Vaccination

• HPV vaccine – prevents the strains most likely to cause cancer and warts
• Hepatitis A and B vaccines – highly effective prevention

Maintain Oral Health

• Good dental hygiene reduces mouth sores and inflammation
• Avoid brushing or flossing immediately before oral sex (can cause tiny cuts)
• Avoid oral sex if you have mouth sores or bleeding gums

The Bottom Line

Oral sex is not risk-free, and the absence of symptoms in you or your partner doesn't guarantee safety. STIs can and do spread through oral sex, often without either partner knowing they're infected.

This doesn't mean you need to avoid oral sex entirely – but it does mean being informed, using protection when appropriate, and getting tested regularly.

Know Your Status

Our comprehensive STI screening can include throat swabs to check for oral infections. If you've had oral sex and haven't been tested recently, now is the time. Book your confidential test today.