A condom is a thin, flexible sheath worn during sex that acts as a physical barrier between partners. It prevents pregnancy by stopping sperm from reaching an egg, and it reduces the risk of sexually transmitted infections by blocking the exchange of bodily fluids and skin-to-skin contact with infected areas. Condoms are one of the most widely available, affordable, and well-studied forms of protection, and they remain the single most effective method for preventing most STIs.
How Condoms Work
The concept is simple: a condom creates a sealed layer between partners so that sperm, vaginal fluids, and blood never make direct contact. This barrier stops sperm from entering the uterus, which prevents pregnancy. At the same time, it blocks viruses and bacteria that cause infections like HIV, chlamydia, gonorrhea, and syphilis. It also covers or lines the skin surfaces involved in sex, reducing exposure to sores or ulcers that can transmit infections through skin contact.
External and Internal Condoms
There are two main types. External condoms (sometimes called male condoms) are rolled onto an erect penis before any sexual contact. Internal condoms (sometimes called female condoms) are inserted into the vagina ahead of time, lining the canal and creating a pouch that collects semen. Both types work on the same barrier principle, but they differ in design, fit, and materials.
With perfect use every time, external condoms are about 98% effective at preventing pregnancy. Internal condoms are about 95% effective with consistent, correct use. In real life, though, people don’t always use them perfectly. Typical use of external condoms drops effectiveness to around 82%, meaning roughly 1 in 5 people relying on them over a full year will experience a pregnancy. The gap between “perfect” and “typical” use comes down to errors like putting a condom on partway through sex, using the wrong lubricant, or not leaving room at the tip.
Materials: Latex, Non-Latex, and Lambskin
Most external condoms sold in the U.S. are made of latex, a natural rubber. Latex condoms are the most widely available, least expensive, and most thoroughly tested option. They’re flexible, strong, and block both sperm and pathogens reliably.
Some people have latex allergies, which can cause itching, redness, or more serious reactions. Non-latex alternatives include polyurethane and polyisoprene condoms. These synthetic materials conduct heat well, warming to body temperature quickly, and many users report preferring how they feel. The tradeoff is that non-latex condoms do break more often during use. A systematic review of clinical trials found that non-latex condoms had breakage rates roughly 2.5 to 5 times higher than latex. Despite that, they still provide effective protection, and health experts consider them a good alternative for anyone who can’t or won’t use latex consistently.
Internal condoms are made from nitrile, a synthetic rubber that’s both affordable and compatible with all lubricant types. Lambskin condoms also exist and offer a natural feel, but they have microscopic pores large enough for viruses and bacteria to pass through. Lambskin condoms can help prevent pregnancy but do not protect against STIs.
Why Lubricant Choice Matters
Using the wrong lubricant is one of the most common ways people accidentally compromise a condom. Oil-based products, including petroleum jelly, lotion, coconut oil, and cooking oils, break down latex rapidly and increase the chance of the condom tearing during sex. Water-based and silicone-based lubricants are safe with every type of condom.
If you’re using a non-latex condom made from polyurethane, nitrile, or lambskin, oil-based lubricants won’t damage the material. But household products like moisturizers or cooking oils can still irritate genital tissue or cause yeast infections, so sticking with lubricants designed for sexual use is a safer bet regardless of condom type.
How to Use an External Condom
Correct use makes the difference between 98% and 82% effectiveness, and the technique isn’t complicated. Following CDC guidelines, the steps are:
- Open carefully. Tear the wrapper at the edge. Avoid using teeth or scissors, which can nick the condom itself.
- Check the direction. The condom should unroll easily away from the tip. If you place it inside-out, discard it and use a new one, since pre-ejaculate may already be on the surface.
- Pinch the tip. Squeeze the air out of the reservoir tip to leave space for semen. Trapped air is a common cause of breakage.
- Roll it all the way down. Unroll the condom from the tip to the base of the erect penis before any genital contact with a partner.
- Remove promptly after finishing. Hold the condom at the base of the penis and withdraw before losing the erection, so the condom doesn’t slip off. Then slide it off carefully and throw it in the trash. Never flush condoms.
Each condom is single-use. Using the same condom for a second round, or switching between types of sex without changing condoms, defeats the purpose.
Storage and Shelf Life
Condoms are durable when stored properly but surprisingly fragile when they’re not. External condoms last 3 to 5 years from manufacture, and internal condoms last about 5 years. Every condom package has an expiration date printed on it.
Heat, sunlight, and humidity are the biggest enemies. Condoms should be stored below 104°F (40°C), away from direct sunlight and fluorescent lighting. Even fluorescent bulbs emit enough ozone to degrade latex within hours of direct exposure. That means keeping condoms in a wallet, glove compartment, or back pocket for weeks at a time is a bad idea. Body heat and friction from daily carry can weaken the material long before the printed date. A cool, dry drawer or nightstand is ideal.
If a condom feels brittle, sticky, or stiff when you open it, or if the wrapper looks damaged or the expiration date has passed, throw it away and use a fresh one.
Quality and Safety Testing
Condoms are regulated as medical devices. In the U.S., the FDA oversees their manufacturing, and condoms must meet international standards that include electronic testing for pinholes, air burst tests to check stretchability and strength, and water leak tests to detect even microscopic flaws. Latex condoms follow one set of international standards, while synthetic condoms follow a separate set tailored to their different material properties. Every individual condom in a production batch is electronically tested before packaging.
What Condoms Don’t Fully Protect Against
Condoms significantly reduce but don’t eliminate the risk of every STI. Infections spread through skin-to-skin contact in areas a condom doesn’t cover, like herpes and HPV, can still be transmitted even with consistent condom use. The condom only protects the skin it physically covers. That said, consistent use still lowers the risk of these infections meaningfully compared to no protection at all.
Condoms also don’t protect against pregnancy or STIs if they break, slip off, or are used inconsistently. When breakage does happen, it’s most often linked to expired condoms, oil-based lubricants on latex, or not leaving space at the tip.