Vaginal Odour Changes: When Could an STI Be a Cause?
Published 26 February 2026 · 9 min read
Vaginal odour can change for a wide range of reasons. Diet, hormonal shifts, hygiene products, menstrual cycle variations and sexual activity can all influence how the vaginal area smells at different times. In some cases, however, a change in vaginal odour may be associated with a sexually transmitted infection.
It is important to understand that not all odour changes are linked to STIs. Many causes are entirely benign and resolve on their own. However, when an unusual smell persists or is accompanied by other changes such as discharge colour or texture, laboratory testing can help identify whether an infection may be contributing.
This article explains which STIs may affect vaginal odour, what other common causes exist, and when laboratory STI screening may be appropriate.
Quick Answer – Can an STI Cause Vaginal Odour?
Yes, certain STIs can contribute to changes in vaginal odour. Infections such as trichomoniasis, chlamydia and gonorrhoea may alter discharge consistency and smell. However, the most common cause of a fishy vaginal odour is bacterial vaginosis, which is not always sexually transmitted.
- •Fishy or strong smell
- •Yellow or green discharge
- •Irritation or discomfort
- •Sometimes no additional symptoms
Bacterial vaginosis is a common cause of fishy odour and is not always classified as an STI.
What Is Considered Normal Vaginal Odour?
A mild vaginal odour is entirely normal and varies between individuals. The vagina has a naturally acidic environment maintained by healthy bacteria, and this can produce a slightly tangy or musky scent. Minor fluctuations in odour are a routine part of vaginal health and do not typically indicate infection.
- •Slightly acidic scent
- •Mild cycle-related changes
- •Temporary changes after intercourse
- •Sweat-related variations
- •No persistent strong smell
A noticeable and persistent change from your normal scent — particularly if accompanied by other symptoms — may warrant further investigation through laboratory testing.
STIs That May Affect Vaginal Smell
Several sexually transmitted infections have the potential to influence vaginal odour. These infections may alter the vaginal environment by changing discharge volume, colour, consistency or smell. The following STIs are most commonly associated with odour changes.
Trichomoniasis
Trichomoniasis is caused by a parasite called Trichomonas vaginalis. It is one of the STIs most frequently associated with a noticeable change in vaginal odour. The infection may produce a strong, fishy smell alongside frothy, yellow-green discharge. Some individuals also experience irritation, itching or discomfort during urination.
Chlamydia
Chlamydia is one of the most commonly reported bacterial STIs in the UK. While many cases are asymptomatic, some individuals notice a change in vaginal discharge that may include a mild, unusual odour. A Chlamydia test can confirm whether the infection is present, even when symptoms are subtle or absent.
Gonorrhoea
Gonorrhoea may cause increased vaginal discharge that can appear yellow or green. In some cases, this discharge may carry an unusual smell. As with chlamydia, many gonorrhoea infections produce minimal or no symptoms, making laboratory testing the most reliable method of detection.
Other Common Causes of Vaginal Odour
Many vaginal odour changes are not caused by sexually transmitted infections. A range of other factors can influence how the vaginal area smells, and these are often temporary or easily explained by lifestyle and hormonal factors.
- •Bacterial vaginosis — an imbalance in vaginal bacteria that commonly causes a fishy odour
- •Yeast infection — may produce a bread-like or slightly sweet smell alongside thick discharge
- •Hormonal fluctuations — changes during the menstrual cycle, pregnancy or menopause
- •Menstrual cycle — a metallic scent during menstruation is common
- •Hygiene products — scented soaps, washes or douches can disrupt vaginal pH
- •Diet — certain foods may temporarily influence body odour, including vaginal scent
When odour changes are persistent or accompanied by unusual discharge, laboratory testing can help distinguish between STI-related and non-STI-related causes, providing a clearer picture of what may be contributing.
When Is STI Testing Worth Considering?
If a change in vaginal odour is persistent, unfamiliar or accompanied by other symptoms, laboratory STI testing can provide useful clarity. Testing is a straightforward and confidential process that can either identify an infection or provide reassurance.
- •Persistent strong odour lasting more than a few days
- •Unusual discharge colour such as yellow or green
- •Pelvic discomfort or pain
- •New sexual partner
- •Unprotected sexual contact
A comprehensive STI screening panel can test for multiple infections at once, helping to identify or exclude the most common causes efficiently.
How Laboratory STI Testing Works
Laboratory STI testing analyses samples in an accredited facility to detect the presence of specific infections. Tests are designed to be accurate and confidential, with results communicated directly to the individual.
- •Self-collected swab for infections such as chlamydia and gonorrhoea
- •Venous blood testing for infections such as HIV and syphilis
- •PCR laboratory analysis for high-sensitivity detection
- •Confidential results delivered securely
- •No referral required
Testing can be arranged at a private sexual health clinic in London. The process is straightforward, and results are typically available within a few working days depending on the laboratory.
Does HIV Cause Vaginal Odour?
HIV itself does not directly cause changes in vaginal odour. The virus affects the immune system rather than the vaginal environment directly. However, a weakened immune system may increase susceptibility to secondary infections — including bacterial vaginosis, yeast infections and other STIs — which can influence vaginal health and odour.
If you are concerned about your overall sexual health status, an HIV blood test can provide clarity. HIV testing is a confidential blood-based test that detects antibodies and antigens, and it can be included as part of a broader screening panel.
People Also Ask
Does fishy smell always mean an STI?
No. A fishy vaginal odour is commonly associated with bacterial vaginosis, which is not classified as a sexually transmitted infection. However, some STIs such as trichomoniasis can also produce a similar smell. Laboratory testing can help distinguish between possible causes and provide clarity.
Can chlamydia cause odour without discharge?
In some cases, chlamydia may contribute to subtle changes in vaginal odour without producing noticeable discharge. Many chlamydia infections are asymptomatic. If you are concerned about any change, laboratory testing can confirm whether an infection is present.
Can hormonal changes affect vaginal smell?
Yes. Hormonal fluctuations during the menstrual cycle, pregnancy, perimenopause and menopause can all influence vaginal odour. These changes are typically temporary and mild. If an unusual smell persists, testing may help rule out other causes.
Should I test if odour is my only symptom?
Odour alone can be worth investigating, particularly if it is persistent, unusual or accompanied by other subtle changes. Some STIs present with minimal symptoms. Laboratory screening can provide reassurance or identify an underlying cause.
How long should abnormal odour last before testing?
There is no set timeframe. If a noticeable change in vaginal odour persists for more than a few days and is not explained by diet, hygiene products or menstrual cycle variations, laboratory testing may be appropriate to rule out infection.
This article is for general information. Laboratory testing is required to confirm any infection. MD.co.uk provides private STI testing services. We do not provide diagnosis, prescriptions or treatment. If you have concerns about your health, please consult a qualified healthcare professional.
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For general information only — not a substitute for professional advice. In an emergency call 999, visit A&E, or call NHS 111.