Can you still pass on STIs if you wear a condom?

Do condoms protect against all STIs?

If you’ve ever wondered whether condoms fully protect you against sexually transmitted infections – or felt confused about why you might still be at risk even when using one correctly – you’re not alone. Condoms are brilliant, but they have limits that are worth understanding.

How condoms protect you

When used correctly and consistently, condoms create a physical barrier against semen, vaginal secretions, and blood – the bodily fluids that carry many STIs. This makes them highly effective against infections that spread this way, including HIV, chlamydia, gonorrhoea. So far, so good. But here’s where it gets more complicated.

Why condoms can’t protect against everything

Some STIs don’t spread through bodily fluids – they spread through skin-to-skin contact. This means they can be transmitted through infected skin on the scrotum, vulva, anus, or surrounding areas that a condom simply doesn’t cover. These can include herpes simplex virus and syphilis. 

This isn’t a reason to panic – condoms still reduce your risk even for these infections by limiting the amount of skin contact involved. But it’s useful to know that even perfect condom use doesn’t eliminate the risk entirely.

Does it matter how you use them?

YES. Condoms only do their job when used correctly, every single time. Some common slip ups that reduce protection include:

• putting a condom on after sexual contact has already started
• removing it before ejaculation
• using one that’s damaged or expired
• Using the wrong size, which can increase the risk of it slipping off or tearing 

Oral sex is also worth mentioning here. Most people don’t use condoms during oral sex, but several STIs – including gonorrhoea, syphilis, and herpes – can be transmitted this way.

What about vaccines and other tools?

• The HPV vaccine offers strong protection against the strains of HPV most likely to cause cancer and genital warts – if you haven’t had it, it’s worth looking into. 
• PrEP (pre-exposure prophylaxis) is a daily medication that’s highly effective at preventing HIV transmission and is available on the NHS. 
• Regular STI testing – especially with new or multiple partners – means that if something is there, you catch it early.

The bottom line

Condoms are one of the most effective tools we have against STIs, and some protection is always better than none. They work brilliantly against fluid-transmitted infections like HIV and chlamydia, and they reduce (although can’t eliminate!)  the risk of skin-to-skin transmitted infections like herpes and HPV. 

References

1. https://www.nhs.uk/contraception/methods-of-contraception/condoms/ 
2. https://www.bashh.org/news/1649/statement_on_who_regional_office_for_europe_revealing_high_rates_of_condomless_sex_among_adolescents/ 
3. https://bhiva.org/wp-content/uploads/2025/01/BASHH_BHIVA_Safer_Sex_Advice_WebFinal120712.pdf 
4. https://www.cdc.gov/condom-use/index.html