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

Oral sex is often seen as a low risk alternative to intercourse. It is lower risk for some infections, but it is not risk free. You can catch or pass on sexually transmitted infections through oral sex, and many of those infections cause few or no symptoms. That is why people are often surprised to test positive after feeling completely fine. This guide explains which infections can spread via oral sex, what signs to watch for, and how to protect yourself and your partners.

How oral sex can transmit infections

During oral sex, bacteria and viruses can move between the mouth, throat and genitals through saliva, genital fluids and contact with the lining of the mouth and throat. Tiny abrasions in the mouth or on the lips can provide an entry point, and infected secretions can infect the throat or the genitals depending on the direction of contact. Because the throat can carry infection silently, someone may pass on an STI without realising.

👉 Worried after unprotected oral sex? Arrange a discreet screen with STI Clinic.

STIs that can spread through oral sex

Gonorrhoea
Very capable of infecting the throat. Many people have no symptoms, but some notice a sore throat or discomfort when swallowing. Throat infection can pass to partners through oral sex.

Chlamydia
Less common in the throat but still possible. Often silent. When symptoms occur, they can resemble a mild sore throat or swollen glands.

Syphilis
Transmitted when a painless sore is present on the mouth, lips or genitals. The sore may be small and go unnoticed. Even after it heals, the infection persists unless treated.

Herpes simplex virus
Cold sores around the mouth are usually HSV 1. They can spread to a partner’s genitals during oral sex. Genital herpes can also spread to the mouth. The first episode can be painful, but some people have very mild symptoms or none at all.

Human papillomavirus
HPV can spread through skin to skin and oral contact. Most infections clear on their own, but some types are linked to cancers of the throat, cervix and anus. Vaccination offers important protection.

HIV
The risk from oral sex is lower than from vaginal or anal sex, but it is not zero. Risk increases when there are mouth ulcers, bleeding gums or other oral lesions.

Trichomonas and hepatitis B
Less commonly transmitted through oral sex, yet still possible under certain conditions.

Why symptoms are unreliable

Many throat infections cause no symptoms at all. When symptoms do appear, they are often mild and easy to dismiss. A tickly throat, brief redness, or swollen glands may not prompt someone to seek testing. This is how infections persist in a community. Relying on symptoms alone is not a safe strategy. Testing is the only way to know your status with confidence.

👉 Prefer certainty over guesswork? Book a confidential test with STI Clinic: STI Clinic.

Signs to take seriously

Although the throat can carry infection silently, the following should prompt testing:

• Persistent sore throat that does not settle
• Redness, ulcers or white patches in the mouth or on the tonsils
• Swollen neck glands
• Painful blisters or sores around the lips or inside the mouth
• Unusual genital discharge after oral contact
• Fever or a flu like illness after a new sexual partner

Remember that absence of these signs does not mean all clear. If you have had a new partner or unprotected oral sex, a planned screen is sensible.

How to reduce the risk during oral sex

• Use condoms for oral sex on a penis. This limits exposure to genital fluids and reduces transmission.
• Use dental dams for oral contact with the vulva or anus. A thin barrier creates an effective protective layer.
• Avoid oral sex if you or your partner have active cold sores, mouth ulcers or visible genital sores.
• Keep up with HPV vaccination if eligible.
• Do not share sex toys, or cover them with a fresh condom between partners or body sites.
• Plan regular screens that include site specific swabs when relevant. If you give or receive oral sex, throat swabs can be part of a comprehensive check.

When to test and what to expect

If you have had unprotected oral sex with a new partner, you can test now and again at the appropriate window periods. For gonorrhoea and chlamydia, throat swabs are usually reliable from about two weeks after exposure. Syphilis and HIV blood tests often require a little more time to become conclusive. A clinician can advise on timing and which tests make sense for your situation.

Testing is quick and discreet. Swabs are usually painless, and results are often available within a few days. If treatment is needed, it is straightforward for most bacterial infections, and there is clear guidance for partner management to prevent ping pong transmission.

👉 Ready to book or need help with timing? Get tailored advice and fast testing at STI Clinic.

Get Tested Early, Stay Safe

Even without symptoms, some STIs can be transmitted through oral sex. Book a confidential test today to know your status and protect yourself and your partner.

Book us online 02071830494

The practical takeaway

Yes, you can get an STI from oral sex even if you feel perfectly fine. Throat infections such as gonorrhoea and chlamydia are often silent. Syphilis can be present without obvious sores. Herpes and HPV can spread through skin to skin contact around the mouth and genitals. The most reliable plan is to use barriers where possible, vaccinate where eligible and schedule regular screens that reflect your sexual practices. That approach keeps you informed, protects your partners, and reduces anxiety.

Knowledge and routine are your best safeguards. Add oral health to the way you think about sexual health, and you will be ahead of most people.

👉 Take the next step with confidence. Book a confidential screen today.