A condom is a thin sheath worn during sex to prevent pregnancy and reduce the risk of sexually transmitted infections (STIs). It is the only form of contraception that does both at the same time. Condoms work by creating a physical barrier that keeps sperm from reaching an egg and blocks the exchange of bodily fluids that carry infections like HIV, chlamydia, and gonorrhea.
Pregnancy Prevention
Preventing pregnancy is one of the two core reasons condoms exist. A male (external) condom prevents pregnancy 98% of the time when used correctly every time. In real-world use, where people occasionally skip a step or use one inconsistently, that number drops to about 87%. Female (internal) condoms are 95% effective with perfect use and about 79% effective with typical use.
The gap between perfect and typical use matters. Common mistakes that lower effectiveness include putting the condom on after sex has already started (reported by 38% of users in one large review), removing it before sex is finished (about 14%), and not switching to a fresh condom when moving between types of sex (83%). Avoiding these habits closes much of the gap between the ideal and real-world numbers.
Protection Against STIs
Condoms are highly effective at blocking infections spread through bodily fluids: HIV, gonorrhea, and chlamydia. Because the barrier prevents semen, vaginal fluid, and pre-seminal fluid from making contact with a partner’s mucous membranes, the risk of transmitting these infections drops significantly with consistent use.
Protection is more limited for infections spread through skin-to-skin contact, including HPV, genital herpes, and syphilis. These can live on skin that a condom doesn’t cover, like the outer vulva, the base of the penis, or the upper thigh. A condom still helps when it covers the specific area where the infection is present, but it cannot eliminate the risk entirely. This is an important distinction: condoms are excellent at blocking fluid-borne infections and partially protective against skin-contact infections.
Use During Anal and Oral Sex
Condoms aren’t only for vaginal sex. The tissue inside the rectum is thinner and more fragile than vaginal tissue, making it especially vulnerable to infections carried in semen and pre-seminal fluid. Using a condom during anal sex is one of the most effective ways to reduce that risk.
Interestingly, condoms may actually perform better during anal sex than vaginal sex in terms of breakage. A clinical study of over 500 participants found that condom failure (slippage or breakage) occurred only 0.7% of the time during anal sex compared to 1.9% during vaginal sex. Researchers attributed the difference to lubricant use: 98.3% of anal sex acts involved condom-compatible lubricant, while only 41.6% of vaginal sex acts did. The takeaway is that pairing a condom with the right lubricant makes a real difference in reliability.
For oral sex, condoms (or dental dams, which are flat sheets of latex) reduce the transmission of STIs like herpes, gonorrhea, and syphilis that can infect the throat.
Types of Condoms and Materials
Most condoms are made from latex, but that’s not the only option. The FDA approves three materials for both pregnancy and STI prevention: latex, polyurethane (a type of plastic), and polyisoprene (a synthetic rubber). Each has trade-offs worth knowing about.
- Latex is the most widely available and affordable. It’s stretchy and strong but can trigger allergic reactions in roughly 4% of the population. It also degrades when exposed to oil-based lubricants.
- Polyurethane is thinner than latex, transfers heat better (which can increase sensation), and has no smell. It’s stronger in storage, handles heat exposure better, and resists oil-based lubricants without breaking down. It tends to fit more loosely.
- Polyisoprene stretches similarly to latex and is a good middle ground for people with latex allergies who still want a snug fit. Like latex, it’s incompatible with oil-based lubricants.
- Lambskin condoms are effective for pregnancy prevention but are not FDA-approved for STI protection. Their natural pores are small enough to block sperm but large enough to let viruses pass through.
Internal (female) condoms are typically made from nitrile, a synthetic rubber. They’re inserted into the vagina or rectum before sex and give the receptive partner more control over protection.
Lubricant Compatibility
Using the wrong lubricant with a condom can cause it to weaken and break. Water-based and silicone-based lubricants are safe with every type of condom. Oil-based lubricants, including coconut oil, vaseline, and many lotions, break down latex and polyisoprene and should only be used with polyurethane or nitrile condoms.
Household products like moisturizer or cooking oil are not safe substitutes for personal lubricant. They can irritate genital tissue and, in the case of vaginal use, increase the risk of yeast infections.
Storage and Shelf Life
A condom that’s been stored badly can fail even if you use it perfectly. Latex condoms have a typical shelf life of three to five years from the date of manufacture, but heat, humidity, sunlight, and even fluorescent lighting can shorten that considerably. The general rule is to keep condoms below 104°F (40°C) and away from moisture.
Storing condoms in a wallet is a common habit, but friction and body heat from daily carry can weaken the material over time. About 19% of condom users in one study reported wallet storage. If a condom feels sticky, stiff, or brittle when you open it, it’s compromised and should be replaced. Always check the expiration date on the wrapper before use.
How to Avoid Common Mistakes
Most condom failures aren’t manufacturing defects. They’re user errors. Beyond the timing mistakes mentioned earlier (putting it on late or taking it off early), a few other pitfalls stand out. About 11% of users open condom packages with sharp objects like scissors or teeth, which can nick the condom without being obvious. Pinching the tip to leave space for semen is a step many people skip, and forgetting it increases the chance of breakage.
Using two condoms at once, sometimes called “double bagging,” creates friction between the layers and actually raises the risk of tearing. One condom, used correctly from start to finish with compatible lubricant, is the most reliable approach.