A condom is a thin, stretchy pouch that fits over the penis (or inside the vagina) to create a physical barrier during sex. That barrier does two things: it keeps sperm from reaching an egg, and it blocks the exchange of body fluids that can carry sexually transmitted infections. Condoms are the only method of contraception that also protects against STIs, including HIV.
How Condoms Work
The concept is simple. A condom prevents direct skin-to-skin contact and stops body fluids from passing between partners. During vaginal sex, this means sperm never enters the vagina. During any type of sex, it means viruses and bacteria carried in fluids have a much harder time finding a new host.
That said, the protection isn’t identical for every infection. Condoms are highly effective against STIs spread through genital fluids, like gonorrhea, chlamydia, and HIV. They’re less effective against infections spread by skin-to-skin contact, like genital herpes and syphilis, because these can be transmitted through areas the condom doesn’t cover.
External vs. Internal Condoms
Most people picture an external condom, sometimes called a “male” condom. It rolls onto an erect penis before sex. This is by far the more common type, available in nearly every pharmacy and convenience store.
Internal condoms (sometimes called “female” condoms) are pouches inserted into the vagina before sex. They’re lined with a flexible ring at each end, one to hold the condom in place inside and one that sits outside the body. Both types reduce the risk of STIs and unintended pregnancy when used correctly every time.
Materials and Latex Alternatives
Most external condoms are made from latex, a natural rubber that’s strong, stretchy, and inexpensive. But roughly 1 to 6 percent of the population has some degree of latex sensitivity, and for those people several alternatives exist.
- Polyurethane condoms are made from thin plastic. They offer similar pregnancy and STI protection to latex, transfer heat well (which some people prefer for sensation), and cost slightly more.
- Polyisoprene condoms are made from synthetic rubber that doesn’t contain the proteins responsible for latex allergies. They’re stretchier than polyurethane and provide comparable protection.
- Natural skin condoms (usually lambskin) can help prevent pregnancy but have tiny pores large enough for viruses to pass through, so they don’t reliably protect against STIs.
Getting the Right Fit
Fit matters more than most people realize. A condom that’s too tight is uncomfortable and more likely to break. One that’s too loose can slip off during sex. The FDA requires all external condoms sold in the U.S. to be at least about 6.3 inches long, but width varies by brand and style.
Standard-size condoms typically fit a penis between 5 and 7 inches long with a girth of 4 to 5 inches. Snug and large options exist for people outside that range. For most people, a standard size works fine, but if you notice frequent slipping or discomfort, check the manufacturer’s sizing guide on the packaging.
How to Use an External Condom
Correct use is straightforward but each step matters. Open the wrapper carefully (teeth and scissors can nick the latex). Place the condom on the head of the erect penis, pinch the air out of the tip to leave room for fluid, then unroll it all the way down the shaft. After sex, hold the base of the condom while pulling out so it doesn’t slip off. Remove it, tie it off if you like, and throw it in the trash. Never reuse a condom.
One common mistake is using the wrong lubricant. Oil-based products like baby oil, petroleum jelly, lotion, and cooking oil break down latex and polyisoprene, dramatically increasing the chance of the condom tearing. Stick with water-based or silicone-based lubricants unless you’re using polyurethane condoms, which are compatible with oil-based options.
Storage and Expiration
Condoms have a shelf life of three to five years from manufacturing, but that number drops fast under bad storage conditions. Heat above 104°F (40°C), direct sunlight, humidity, and even prolonged exposure to fluorescent lighting can weaken latex in a matter of hours. A condom that’s been sitting in a wallet, glove compartment, or back pocket for weeks has likely been subjected to enough heat and friction to compromise it.
Always check the expiration date on the wrapper before use. If the packaging feels brittle, sticky, or damaged, toss it. A degraded condom is far more likely to break during sex.
What Condoms Don’t Do
Condoms significantly reduce risk, but they don’t eliminate it entirely. They’re most effective against fluid-borne infections and pregnancy. They’re less protective against skin-to-skin STIs that can live on areas not covered by the condom, like the surrounding skin of the genitals or upper thighs. Using condoms consistently still reduces herpes and HPV transmission compared to unprotected sex, but the protection isn’t as complete as it is for something like HIV or chlamydia.
For pregnancy prevention, the gap between perfect use and typical use tells the real story. Perfect use means a new condom, applied correctly, for every act of intercourse. Typical use accounts for the reality that people sometimes put them on late, use expired ones, or skip them altogether on occasion. The difference between those two scenarios is significant, which is why consistency matters as much as technique.