STIs and Oral Sex: What Spreads, How Risky It Is and How to Protect Yourself

Oral sex is not the safe alternative many people assume. Many sexually transmitted infections (STIs) spread through it — though for HIV, the risk is little to none. Using a condom, dental dam or other barrier every time lowers the chance of giving or getting an infection.

How common it is

Oral sex means using the mouth on a partner's penis (fellatio), vagina (cunnilingus) or anus (anilingus). It is common:

• More than 85% of sexually active adults aged 18–44 reported oral sex at least once with an opposite-sex partner.
• In a separate survey during 2011–2015, 41% of teenagers aged 15–19 reported oral sex with an opposite-sex partner.

Which infections spread this way

Anilingus can also pass on hepatitis A and B, parasites such as Giardia, and bacteria such as E. coli and Shigella.

How it happens:

• Giving oral sex to a partner with a genital or anal infection can cause an infection in the mouth or throat.
• Receiving oral sex from a partner with a mouth or throat infection can cause a genital infection.
• One person can be infected in more than one place at once — the throat and the genitals, for example.
• Some infections passed this way, including syphilis, gonorrhea and intestinal infections, can spread through the body.
• Many STIs cause no symptoms, so people can pass them on without knowing they have them.

The risk depends on the infection, the type of sex and how often. Poor oral health (tooth decay, gum disease, bleeding gums, oral cancer), sores in the mouth or on the genitals, and contact with pre-ejaculate or ejaculate may raise the risk — but no studies show whether they actually do.

Is it safer than vaginal or anal sex?

For HIV, yes: the risk from oral sex, giving or receiving, is much lower than from anal or vaginal sex — perhaps extremely low, though the exact risk is hard to know. For other STIs, not necessarily. Comparisons are hard because most people who have oral sex also have vaginal or anal sex, and few studies compare oral sex on the vagina or anus with oral sex on the penis. In one study of gay men with syphilis, 1 in 5 reported having only oral sex.

A throat infection is not a minor one:

• Chlamydia or gonorrhea in the throat may be less harmful than in the genitals or rectum, but it may raise the risk of getting HIV and makes it easier to pass the infection on through oral sex. That matters most for gonorrhea, which is harder to treat in the throat, and throat gonorrhea may spread through the body.
• Syphilis and HIV acquired through the throat can cause the same health problems as those acquired genitally.
• Some types of HPV in the mouth and throat may develop into oral or neck cancer.

Protecting yourself

• On a penis: a non-lubricated latex condom; a polyurethane (plastic) condom if either partner is allergic to latex.
• On a vagina or anus: a dental dam — or cut open a condom into a square and place it between mouth and body.
• The only certain way to avoid STIs is not to have vaginal, anal or oral sex. Otherwise, a long-term mutually monogamous relationship with a partner who has tested negative, and latex condoms used correctly every time, lower the risk.

Get tested regularly if you are having sex, and tell your provider about everything that could put you at risk — including oral sex. Talk with your partners about STIs, too. Free and low-cost testing is listed at gettested.cdc.gov.

Sources

Based on "About STI Risk and Oral Sex," Centers for Disease Control and Prevention; a work of the United States government in the public domain.