How Condoms Prevent HIV

The human immunodeficiency virus (HIV) is a sexually transmitted virus that can be effectively prevented by using appropriate barrier methods such as condoms and dental dams. This is because HIV is only transmitted by certain bodily fluids, not by skin-to-skin contact.

It is easier to prevent than viruses like herpes that are spread from skin to skin. Pre-exposure prophylaxis (PrEP) can also be used to reduce the risk of sexual transmission of HIV.

This article will discuss how HIV is transmitted, how condoms can be used to prevent HIV, when to use a condom, and how to use a condom most effectively.

Using Condoms to Prevent HIV

Verywell / Theresa Chiechi

How HIV Is Transmitted

HIV is a virus that can be transmitted by exposure to certain types of bodily fluids. If fluids containing HIV get into the body through openings in the skin or through contact with mucosal surfaces (such as the eyes, vagina, or rectum), they can lead to infection.

Bodily fluids that can contain enough HIV to transmit the virus include:

  • Blood
  • Semen and pre-cum
  • Vaginal secretions
  • Breast milk
  • Rectal secretions

What Doesn’t Transmit HIV

Saliva, tears, and sweat cannot transmit HIV. HIV cannot be transmitted through casual contact.

HIV can only be transmitted through exposure to infectious secretions. This can occur during sex, through shared needles or drug paraphernalia, or workplace exposure to blood and secretions. Universal precautions have largely eliminated the transmission of HIV in American healthcare settings.

How Condoms Prevent HIV

Condoms prevent HIV by blocking exposure to potentially infectious bodily fluids during sex. External condoms, when used properly, keep both semen and pre-cum contained and prevent them from reaching a person’s sexual partner during anal sex, vaginal intercourse, or fellatio.

Internal condoms, also known as female condoms, protect the vagina from semen and pre-cum and the penis from exposure to vaginal secretions.

Only latex, polyurethane, and polyisoprene condoms are effective at preventing HIV transmission and other sexually transmitted infections (STIs).

Lambskin condoms may have pores that are large enough for the virus to pass through. They should only be used for pregnancy prevention by mutually monogamous couples who have both tested negative for HIV and other STIs.

The Lowdown on Dental Dams

Dental dams are barriers used to prevent the transmission of viruses during oral sex. Placing this latex barrier between your mouth and your partner’s genitals can help to prevent STIs. Dental dams can be used for both cunnilingus (oral sex involving the vulva and vagina) and rimming (oral sex involving the anus).

Dental dams can be purchased. They can also be made from condoms and gloves. It’s very easy to make a dental dam from a latex or polyisoprene condom. Just cut the tip off the condom and then cut down one side. Now you have a dental dam ready to use.

When to Use a Condom

To reduce the risk of transmission of HIV and other STIs to the greatest extent possible, condoms can and should be used for any type of sexual activity involving a penis.

The exception is for couples who have both tested negative for HIV and other STIs and are only sexually active with each other. However, the most recent test for both members of the couple should have been after the window period for any possible previous exposure.

Anal Sex

Unprotected, receptive anal sex is one of the riskiest behaviors for the transmission of HIV. This is because the rectal tissues are highly susceptible to HIV, and both semen and pre-seminal fluid can have high concentrations of HIV.

Consistently and correctly using a condom for anal sex can substantially reduce the risk of HIV transmission through anal sex by as much as 70%. For condoms to be this effective, they must be used every time you have anal sex. It is also important to use an appropriate sexual lubricant.

Vaginal Sex 

Around the globe, vaginal intercourse is the leading source of HIV transmission. It is also common in some areas of the United States.

Vaginal sex is most risky for the person being penetrated, but vaginal secretions can contain HIV, and transmission can go in both directions. Consistently and correctly using condoms for vaginal sex, along with a water- or silicone-based lubricant, can significantly reduce the risk of HIV transmission during vaginal sex.

Researchers estimate 80% protection against HIV for consistent condom users in general. There is some suggestion that 90% to 95% protection is possible for people who use them correctly all the time.

Oral Sex

While it is theoretically possible to transmit HIV during oral sex, it is not a major source of HIV transmission. Oral sex includes cunnilingus (oral/vaginal sex), fellatio (oral/penile sex), or rimming (oral/anal sex).

Factors that could increase the risk of oral sex include the viral load of the person receiving oral sex. Viral load is how much virus is in vaginal, rectal, or penile secretions.

Mouth sores and injuries to the mouth and throat could also increase the risk of transmission, but the risk is still considered low.

That said, HIV is not the only STI that can be transmitted through oral sex. Using condoms for oral/penile sex and dental dams for oral/anal or oral/vaginal sex can reduce the risk of not just HIV, but other sexually transmitted infections.

HIV Transmission Between Females

There is very little data suggesting that HIV can be transmitted between females who are having sex with other females (in which there is no penile penetration). While both menstrual blood and vaginal secretions can contain HIV, reported transmissions between females during sexual activity are extremely rare.

However, women who have sex with women may have other risk factors for HIV. Women who have sex with women may also have sex with men, use injection drugs, or exchange sex for drugs or money.

These activities are as risky for women who have sex with women as they are for women who do not. Therefore, it is important to engage in appropriate HIV-prevention behaviors such as safe sex and not sharing needles.

How to Use Condoms Most Effectively

How do you use condoms most effectively? The trick is to use them consistently and correctly every time you have sex. That doesn’t mean you should give up hope if you fail to use a condom once. You can always do better the next time. STIs aren’t transmitted every time you have sex, so it’s always worthwhile to use protection.

External Condoms

External condoms, also known as male condoms, are the most common barrier used for safer sex. They can be used for penile/anal sex, penile/vaginal sex, and penile/oral sex to make those activities safer.

Condoms should be put on with clean hands as soon as the penis becomes erect and before engaging in any sexual penetration that could lead to exposure to semen or pre-cum.

Steps for putting on an external condom are:

  1. Check that the condom hasn’t expired by looking at the date on the package. You should also be able to feel an air bubble, which will show that the package hasn’t been damaged.
  2. Wash your hands and carefully open the condom package.
  3. Figure out which way is up. The condom should go on so that it unrolls easily down the penis. It goes on like a hat, not like a shower cap that unrolls from the inside. If you start to put the condom on upside down, throw it away and start again.
  4. Unroll the condom a little bit, so there is room at the tip. Pinch the tip to get rid of any air, and then hold that space when you place the condom on the penis. It can help to put a tiny bit of lubricant inside the condom if you have issues with air bubbles.
  5. Unroll the condom the rest of the way to the base of the penis.
  6. Check for trapped air. If the condom feels like a balloon, you may be at risk of breakage during sex. You can remove the air from the condom by smoothing the air out gently from tip to base.

After you are done having sex, the person who has ejaculated should hold the condom as they withdraw from the mouth, vagina, or rectum to avoid slippage. Then it can be discarded in the trash.

Internal Condoms

Internal condoms, also known as female condoms, are placed inside the vagina before vaginal intercourse. Some people prefer these condoms to external condoms for a variety of reasons, including:

  • They can be inserted earlier during sex or even before sex.
  • An erection or consistent erection isn’t required for them to be effective.
  • They are not made of latex, which is helpful for people with latex allergies.
  • They are more comfortable for some people who have an uncircumcised penis.

While some individuals have also used internal condoms for anal sex, there is a lack of research evaluating their safety and effectiveness for that purpose.

To use an internal condom:

  1. Check the expiration date on the condom and make certain the package hasn’t expired and hasn’t been damaged.
  2. Wash your hands and carefully open and remove the condom from the package.
  3. The internal condom has a closed end and an open end. There are flexible rings at both ends of the condom, with the thicker ring at the closed end. The closed end will be placed inside the vagina.
  4. Find a comfortable position, squeeze the sides of the ring for the closed ends together with your thumb and forefinger, and insert the ring into the vagina. This is like inserting a tampon or menstrual cup.
  5. Keeping the open end outside your body, insert a finger into the condom and push the inner ring as far up as it can go until it sits next to the cervix. The condom will expand naturally.
  6. Make certain the condom isn’t twisted.
  7. When starting to engage in intercourse, guide your partner to make certain they penetrate inside the condom and that the outer ring stays outside the body. If you feel the ring slip inside, stop intercourse. The same is true if your partner penetrates between the condom and your skin.

After you are done having sex, gently twist the outer ring to reduce the risk of leakage. Then pull the condom from the vagina and discard it. Internal condoms should not be reused once they have been removed.


Condoms are very effective in preventing HIV transmission when used consistently and correctly. They provide a barrier between bodily fluids that can contain HIV and body surfaces where the virus can enter a sex partner’s body.

To prevent HIV, condoms should be used during any sexual activity involving a penis. There are two types of condoms—external (male) condoms and internal (female) condoms.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Elizabeth Boskey, PhD
Elizabeth Boskey, PhD, MPH, CHES, is a social worker, adjunct lecturer, and expert writer in the field of sexually transmitted diseases.