Barriers: condoms, internal condoms, dams and gloves

External condoms

Latex or polyisoprene sheaths worn on the penis or on an insertive toy. Cochrane review evidence (Weller and Davis-Beaty, updated) puts consistent, correct use at around 80 percent effective at preventing HIV transmission in serodiscordant heterosexual couples — the figure reflects real-world consistency, not per-act failure. For pregnancy: 2 percent failure with perfect use, 13 percent with typical use over a year (Trussell, Contraceptive Technology).

Correct use:

1. Check the expiry date and that the package has an air pocket.
2. Open with fingers, never teeth or scissors.
3. Pinch the tip to remove air before rolling on — trapped air is the main cause of breakage.
4. Roll down fully, over a fully erect penis, before any genital contact. Pre-ejaculate carries HIV and other pathogens and can carry sperm.
5. Use fresh lubricant on the outside; add more during longer sessions, since friction against a drying condom is the second main cause of breakage.
6. Hold the base while withdrawing, while still erect.
7. New condom for every act, every partner, and every change of orifice.

Never double up — condom-on-condom friction increases failure. Polyurethane condoms suit latex allergy but break slightly more often; polyisoprene is a closer substitute for latex feel. Lambskin condoms prevent pregnancy but have pores that pass viruses, so they do not prevent HIV, hepatitis B or herpes.

Size matters for reliability, not vanity: too tight breaks, too loose slips. Nominal width typically ranges 49–60 mm.

Internal condoms

A nitrile pouch inserted into the vagina or rectum, usable up to several hours in advance, and controlled by the receptive partner. Typical-use pregnancy failure is 21 percent per year, perfect use 5 percent. Advantages: no erection needed, compatible with oil-based lubricant, nitrile so no latex issue, and the external ring covers some vulval skin, which may reduce herpes and HPV exposure. When used for anal sex, most guidance advises removing the inner ring.

Dams

A sheet of latex or polyurethane placed over the vulva or anus for oral sex. Direct efficacy trial evidence is thin — this is an area of genuinely limited research — but the mechanistic barrier rationale is the same as for condoms, and dams are recommended by BASHH and CDC for reducing herpes, HPV, syphilis, gonorrhoea and hepatitis A exposure during oral-vulval and oral-anal contact.

Improvise by cutting an unrolled condom lengthwise, or cutting the fingers off a glove and slitting one side. Do not flip a dam over mid-use. Non-microwavable cling film is used in some settings and is recommended by several sexual health services as better than nothing, though it is not manufactured or tested for the purpose.

Gloves

Nitrile or latex gloves for manual sex. They cover hangnails, cuts and rough skin, prevent transfer of bacteria between sites, make cleanup simple, and are essential for fisting. Nitrile is the default choice: no latex allergy risk and compatible with all lubricants. Change gloves between partners and between orifices.

What breaks a barrier

Oil is fine with nitrile, polyurethane and polyisoprene. Only latex is affected.

If a condom breaks

1. Stop and withdraw.
2. Consider emergency contraception — the copper IUD is the most effective option, up to 5 days; ulipristal acetate up to 120 hours; levonorgestrel up to 72 hours.
3. Consider HIV PEP — must start within 72 hours, sooner is better.
4. Test for STIs after the appropriate window (see the testing article).
5. Do not douche the vagina or rectum; it increases mucosal damage rather than reducing risk.

Sources

• Weller SC, Davis-Beaty K. "Condom effectiveness in reducing heterosexual HIV transmission." Cochrane Database of Systematic Reviews.
• Trussell J. "Contraceptive failure in the United States." Contraception, and Contraceptive Technology, 21st edition.
• CDC. "Condom effectiveness" and STI treatment guidelines, current edition.
• BASHH. UK national guidelines on safer sex advice, current edition.
• WHO/UNFPA. Male and female condom technical specifications and prequalification, current editions.
• Wilkinson D et al. "Nonoxynol-9 for preventing vaginal acquisition of HIV infection." Cochrane, and WHO/CONRAD technical consultation, 2002.

Last reviewed: August 2026.