Condoms are not full-proof in preventing STIs. Using them correctly can help reduce the chance of transmission.

rows of royal blue external condoms wrapped in silver foil against a light blue backgroundShare on Pinterest
Yaroslav Danylchenko/Stocksy United

Ready for some tough love about (external) love gloves? They aren’t 100 percent effective at preventing sexually transmitted infections (STIs) or sexually transmitted diseases (STDs).

That means there’s some possibility that you use a condom during sex *and* still transmit or contract an STI.

Here’s what you need to know.


Although these acronyms stand for different things, they can be used interchangeably.

Technically, disease is the term used when symptoms are present, while infection is the term used when symptoms aren’t present.

Over the last decade, health practitioners have made a push to use the term STI more in nod to the fact that the majority (around 66 percent) of sexually transmitted viruses and conditions are asymptomatic.

There are two main types of condoms: external and internal. External condoms cover the shaft of a penis or dildo, and internal condoms (formerly known as ‘female condoms’) line the internal vaginal or anal canal.

Here, we’re talking about external condoms — specifically external condoms made of latex, polyurethane, or polyisoprene.

There are external condoms made out of lambskin, but we’re NOT including those here. Why? Because lambskin contains porous holes that semen 肠补苍’迟 fit through, but sexually transmitted infectious particles can.

This means lambskin condoms 肠补苍’迟 ever reduce STI transmission.

To understand how STI transmission might happen during condom use, you have to understand how effective condoms are and how STIs are transmitted.

Buckle-up for a little sex ed lesson with Felice Gersh, MD, the author of “PCOS SOS: A Gynecologist’s Lifeline To Naturally Restore Your Rhythms, Hormones and Happiness.”

How effective condoms are

When used perfectly, external condoms are estimated to be 98 percent effective. The missing 2 percent here accounts for the fact that some condoms rip or break, according to Gersh.

Most pleasure-seekers, however, don’t always put the condom on at the right time, in the right way, or remove it correctly. With typical use, external condoms are 85 percent effective.

How STIs spread

All STIs spread through skin-to-skin contact or through transmission of bodily fluids. (And, in some cases, both.)

Spread through skin-to-skin contactSpread through bodily fluids
herpes simplex virus (HSV)
molluscum contagiosum
hepatitis B

Even when used perfectly, condoms are pretty darn effective at preventing the transmission of STIs through bodily fluids.

However, even when used perfectly, “condoms don’t cover all the genital skin,” Gersh says.

This means, if an STI spread through skin-to-skin contact left viral particles on a part of the body the condom *doesn’t* cover, transmission is possible.

For example, let’s assume someone has a herpes outbreak on their testicles. This part of the body isn’t covered by a condom, even if the condom is being used correctly. So, if their testicles touch someone’s vulva or anus during sex, the virus could be transmitted.

To be clear: Someone can have an STI that can be spread through skin-to-skin contact, even if they don’t ‘look’ like they have an STI.

“There are STIs spread through skin-to-skin contact that create visible lesions or warts, but there are also STIs spread through skin-to-skin contact that are totally invisible to the person who has it, and their sex partner(s),” Gersh says.

Learn exactly how to use a condom correctly, then do so!

Buy a condom that fits

This is not the time to over-estimate or under-estimate your measurement. A loose condom is more likely to slip off, while a tight condom is more likely to break.

Andy Duran, the education director with Good Vibrations, recommends going to your local sex shop, buying a variety of condoms, and exploring which is the best fit for you.

“Usually, sex shops will have single condom options, so you don’t have to buy a whole box,” he says.

Good to know!

Store them correctly

Condoms need to be stored in a cool, dry place, Duran says.

“You may have seen someone store a condom in a wallet in a movie, but you actually don’t want to store it there, because that place creates too much friction and heat,” he adds. “The best place to keep it is in the box in a drawer.”

Check the expiration date

The expiration date on condoms isn’t just decoration. It needs to be abided by.

“If you check the date, and it’s still good, you’re ready to go,” Duran says.

Use your fingers to open the packaging

“Don’t try to open the condom with your teeth,” Duran suggests. “Doing so can cause a perceptible or imperceptible tear.”

Put the condom on at the right time

That condom needs to be put on before any bit brushing or bumping starts.

STIs can be transmitted during outercourse, grinding, tribbing, and scissoring, not just penis-in-vagina or penis-in-anus intercourse.

“Transmission is possible if there’s been any kind of genital-to-genital contact or fluid exchange,” Gersh says.

Roll it right

“Condoms aren’t reversible,” Duran says. “So you want to make sure that you put it the right way.”

If you start to put it on and realize you put it on the wrong way, *don’t* just flip it over and try again. Instead, Duran recommends throwing it out and starting with a new one.

While rolling the condom on, be sure to keep the little space at the top. (This is known as the ‘nipple’ or ‘reservoir’ of the condom.)

“The little space at the tip of the condom is where the ejaculate goes,” he says. “If you don’t have this space, the ejaculate can cause the condom to tear.” Ugh.

Remove it, then toss it

Take it off as soon as you or your partner(s) ejaculate.

“After you take it off, make sure you tie it off to keep fluids from spilling out,” Duran says. “Dispose of it in the trash can, because they aren’t flushable.”

Try implementing these three tips.

Know your STI status

Specifically: Your current STI status for all STIs.

That means getting tested for anal and oral STIs if you have or are planning to engage in oral or anal sex.

Gersh recommends all sexually active people get tested once per year or before any new bone buddy — whichever happens first.

Understand the limitations of testing

Did you know that the Centers for Disease Control and Prevention (CDC) recommends against testing for herpes unless there’s a lesion present? Did you know that there’s currently no way to test people assigned male at birth (AMAB) for HPV?

The bad news: Both of these things are true. The good news: Now you know this information, you can take additional precautions.

For example, you might ask a potential partner if they specifically asked to get tested for HSV and what their results were. Or, you may ask if they’ve ever kissed or received oral sex from someone with a cold sore (a type of herpes), to their knowledge.

“It’s not a bad idea to ask a potential [AMAB] partner if any of their past partner’s had a confirmed case of HPV or cervical cancer or pre-cancer,” Gersh adds.

Talk with your potential sexual partner(s) about their STI status

And that doesn’t just mean people you want to have vaginal or anal intercourse with.

“STIs can be transmitted during sex acts, such as oral sex, too,” Gersh explains.

Generally, Duran recommends asking someone what their STI status is at the same time that you share your own.

“This can keep you from coming in an accusatory way and emphasizes that it’s a shared decision,” he says.

You might say:

  • “Before we have sex I just want to share that the last time I got tested was [X] and I’ve had [X] partners since then. When were you last tested?”
  • “Do you have any interest in getting STI tested together before we have sex?”

To be clear: “You can absolutely have sex with someone with an STI,” says Duran. “Knowing status is important because it allows you to use that information to make an informed decision about safer sex practices.”

Getting tested immediately after potential exposure won’t tell you if an STI transmitted to you by the partner(s) you just had sex with, Gersh says.

(Though it could tell you if a previous partner transmitted one or more STIs.)

Why? Because all STIs have an incubation period during which the body “notices,” and then creates antibodies in response to the infection.

“These antibodies are what you’re looking for on a test, and it takes time for these antibodies to become noticeable,” Gersh says.

The incubation period for STIs varies. For chlamydia, gonorrhea, and trichomoniasis, the incubation period is 1 to 4 weeks. For syphilis, HIV, and herpes, the incubation period ranges from 2 weeks to 6 months.

“The best move is to get tested after 2 weeks, then again a few months later,” Gersh says.

The short answer: What your doctor or healthcare professional tells you to do.

If you receive a positive result, the doctor will probs prescribe a dose of antibiotics in the case of curable STIs (like syphilis, gonorrhea, chlamydia, and trichomoniasis).

Or they might prescribe a method that can help you manage the symptoms of treatable STIs (like HSV and HIV).

Your move: Take this medication.

The doctor will also tell you to abstain from all or some sex acts for a certain period of time, which you should do in order to reduce the risk of transmission.

Next, it’s a good move to talk with any past partners you’ve had that may have also been exposed.

“If you have access to the people still, make the call or send the text,” Duran says. “If you got a gonorrhea diagnosis, for example, and had five partners since your last test, you want to check in with all of [them] to let them know that they may have been exposed, so they can get tested as well.”

How to tell a partner about possible exposure

Keep it simple and free of blame or judgment. You might say:

  • “Hey! Just wanted to let you know that I got tested for [X]. My doctor recommended that I let any recent partners know, so they can get tested, too.”
  • “Hi! I went in for my annual STI screening and found out I have [X]. My doctor told me it can be spread even if a condom was used, so you might want to get tested to be safe.”

Condoms are pretty effective at preventing STI transmission, but they’re not perfect.

But that doesn’t mean you should forgo the barrier altogether. It just means that you should practice putting condoms on and have a few extra convos with any new boo before boning!

Gabrielle Kassel is a New York-based sex and wellness writer and CrossFit Level 1 Trainer. She’s become a morning person, tested over 200 vibrators, and eaten, drunk, and brushed with charcoal — all in the name of journalism. In her free time, she can be found reading self-help books and romance novels, bench-pressing, or pole dancing. Follow her on Instagram.