Condoms, and why they fail

Condoms are highly effective in perfect use and considerably less so in typical use, and the entire gap consists of identifiable, avoidable errors.

The errors that studies actually find

Research documenting condom use errors reports a consistent list.

Applying it after penetration has already begun, which is the most common and which forfeits protection against infections transmitted by contact.

Removing it before sex has finished.

Failing to leave space at the tip and to expel air, which is the main cause of breakage.

Unrolling it before placing it on, which makes it impossible to fit properly.

Putting it on inside out, then flipping it over and using it, which transfers fluid.

Using oil-based lubricant with latex, which degrades it within minutes.

Using no lubricant at all, which increases friction and breakage.

Reusing one.

Using two at once, which increases friction between them and makes failure more likely.

Opening the packet with teeth or a fingernail.

Storing them in a wallet or a hot car for months, where heat and abrasion degrade them.

And not checking the expiry date.

Fit

Underestimated as a factor.

A condom that is too tight is more likely to break and is more likely to be abandoned; one that is too loose slips off.

Sizes vary considerably by manufacturer, in both length and, more importantly, nominal width.

Studies of poor fit find it associated with breakage, slippage, reduced sensation and reduced likelihood of consistent use, which makes trying different sizes a genuine intervention rather than a marketing exercise.

Materials

Latex is the standard, is effective and causes allergy in a minority — which can be significant and which is worth knowing about before it manifests.

Polyisoprene is a synthetic alternative for latex allergy, feels similar and is compatible with the same lubricants.

Polyurethane is thinner, conducts heat, is compatible with oil-based lubricant, and has somewhat higher breakage and slippage rates in studies.

Lambskin prevents pregnancy and does not prevent infection transmission, since the membrane is porous to viruses — a point that is genuinely not widely known.

Internal condoms, worn inside the vagina or anus, are made from nitrile, can be inserted in advance, and are compatible with any lubricant.

What they protect against and what they do not

Highly effective against infections transmitted in fluids: HIV, chlamydia, gonorrhoea, trichomonas and hepatitis B.

Less effective against infections transmitted by skin contact — herpes, HPV and syphilis — because the virus or bacterium may be present on skin the condom does not cover.

Which is not an argument against using them but a reason not to assume complete protection, and an argument for vaccination against HPV and hepatitis B alongside.

When one breaks

What to do, in order.

Do not douche or use anything internally, which does not help and may increase risk.

Consider emergency contraception, which is more effective the sooner it is taken and which is available from pharmacies in most countries.

Consider post-exposure prophylaxis for HIV if there is a relevant risk, which must be started within seventy-two hours and ideally much sooner, through emergency or sexual health services.

Arrange testing at the appropriate window period, which means the test is not immediate.

And discuss it with the other person, since decisions here affect both.

Getting people to use them

The behavioural problem, which matters more than the technical one.

Reduced sensation is the most cited reason for not using them, and is substantially improved by correct size and adequate lubricant inside as well as outside.

Interruption is the second, and is addressed by making application part of the encounter rather than a pause in it.

Negotiation is the third, and is where most non-use actually originates.

Deciding in advance, carrying them, and treating it as a fixed position rather than a negotiation removes the in-the-moment discussion, which is the one nobody wins.

And a partner who resists using one, or who removes one without agreement, has told you something important — the latter is a violation of consent and is recognised as such in a growing number of jurisdictions.

Alongside other methods

The dual approach is standard advice for good reason.

Condoms plus a long-acting method gives near-complete pregnancy protection plus infection protection, which neither achieves alone.

And people using highly effective contraception frequently stop using condoms without a corresponding change in infection risk, which is a well-documented pattern and a reasonable thing to think about explicitly rather than by drift.

General information only, not medical advice. Consult a sexual health service or pharmacist about emergency contraception and post-exposure prophylaxis, which are time-critical.