Is It Normal for Vaginal Odour to Change With an STD?

A persistent change in vaginal odour can indicate bacterial vaginosis, trichomoniasis, chlamydia, or other infections. Testing is the only reliable way to identify the cause and guide treatment.

A change in the way you smell is personal, and it can be difficult to talk about. Many women put off getting checked because they feel embarrassed, or because they assume the change is normal.

Sometimes it is normal. Vaginal odour shifts with your menstrual cycle, diet, exercise, and even stress. But when the change is persistent, strong, or accompanied by unusual discharge, it may indicate an infection that needs treatment.

If you already suspect something is wrong, walk-in testing is available seven days a week at our Harley Street clinic. You do not need a GP referral.

What does a normal vaginal odour smell like?

Healthy vaginal odour varies between women and changes throughout the menstrual cycle, but it should not be strong, fishy, or foul. A mild, slightly acidic or musky scent is typical. The vagina is home to billions of lactobacillus bacteria that maintain an acidic pH (3.8-4.5), and this natural balance produces a subtle smell that most women recognise as their own baseline.

Temporary changes are common after exercise, during menstruation, after sex, or when wearing tight clothing for extended periods. These typically resolve within a day or two without treatment.

When odour changes are persistent, getting stronger, or accompanied by other symptoms, that is when clinical assessment becomes worthwhile.

"Changes in vaginal odour are one of the most common reasons women visit our clinic. In the majority of cases, testing identifies a treatable cause within days. The important thing is not to delay."

Mr Hikmat Naoum, Consultant Gynaecologist, GMC 3047637

Which STIs and infections cause vaginal odour?

Not every infection that causes vaginal odour is sexually transmitted. Bacterial vaginosis, the most common cause of fishy vaginal smell, is technically not an STI, though sexual activity can trigger it. Here is what to look for.

Bacterial vaginosis (BV)

BV is the most frequent cause of abnormal vaginal odour in women of reproductive age (NICE CKS, 2024). It produces a distinctive fishy smell that often becomes stronger after sex and during menstruation. The smell comes from amines released when the normal lactobacillus bacteria are displaced by anaerobic organisms like Gardnerella vaginalis.

BV is not classified as an STI, but it is more common in sexually active women, women with new or multiple partners, and women who douche. It often produces a thin, greyish-white discharge alongside the odour.

Testing for BV is straightforward. We offer Gardnerella testing by PCR swab at £120.63, with results in 1-3 days. A dedicated bacterial vaginosis swab is £105.

Trichomoniasis

Trichomoniasis is caused by a parasite called Trichomonas vaginalis and is a confirmed STI. It produces a strong, unpleasant odour often described as musty or somewhat fishy, distinct from the BV smell. The discharge is typically yellow-green and frothy.

Many women with trichomoniasis also experience vulval soreness, itching, and discomfort during urination or sex. However, up to 50% of women with trichomoniasis have no symptoms at all (BASHH, 2024).

A trichomoniasis PCR test costs £120.63, with results in 1-3 days. Treatment is a short course of antibiotics.

Chlamydia

Chlamydia does not always cause a noticeable odour, but in some women it produces a mildly unpleasant smell alongside changes in discharge. When chlamydia does cause odour, it is often less distinctive than BV or trichomoniasis, making it easier to dismiss.

The bigger concern with chlamydia is what happens when it goes untreated. It is the most common bacterial STI in the UK (UKHSA, 2024) and is frequently asymptomatic. Untreated chlamydia can lead to pelvic inflammatory disease, chronic pelvic pain, and fertility problems.

Chlamydia and gonorrhoea PCR testing costs £103.75, with results in 1-3 days.

Gonorrhoea

Gonorrhoea can cause a change in vaginal discharge, sometimes with a subtle odour, but it is not typically known for producing a strong smell. In women, gonorrhoea symptoms often overlap with other infections, which is why testing is more reliable than symptom-matching.

Forgotten tampon or foreign body

This is more common than you might expect, and it produces one of the strongest and most unpleasant vaginal odours. A retained tampon creates an environment for rapid bacterial growth. If you notice a sudden, severe smell and cannot account for it, a forgotten tampon is worth considering. A GP or walk-in clinician can check and remove it quickly.

Vaginal odour: what the smell may indicate

Odour type	Possible cause	Other symptoms	STI?
Fishy, worse after sex	Bacterial vaginosis	Thin grey-white discharge	No (but linked to sexual activity)
Musty/fishy, strong	Trichomoniasis	Yellow-green frothy discharge, itching	Yes
Mild, slightly off	Chlamydia	Increased or changed discharge	Yes
Foul, very strong	Retained foreign body	Heavy discharge, possibly blood-stained	No
Yeasty, bread-like	Thrush (candidiasis)	Thick white discharge, itching, soreness	No
Metallic	Menstruation or light bleeding	Blood-tinged discharge	No

This table is a guide, not a diagnostic tool. Infections overlap in their symptoms, and several STIs produce no odour at all. Testing is the only way to confirm the cause.

When vaginal odour is not an STI

Thrush (vaginal candidiasis) produces a yeasty smell with thick, white, cottage-cheese-like discharge. It is caused by an overgrowth of Candida fungus and is not sexually transmitted, though it is more common after antibiotics, during pregnancy, and in women with diabetes.

Hormonal changes during menopause can thin the vaginal walls (vaginal atrophy) and alter the bacterial balance, sometimes producing new or different odours. This is not infection-related but can be distressing.

Poor hygiene is rarely the cause. In fact, over-washing with scented products, douching, or using vaginal deodorants disrupts the natural bacterial balance and can make odour worse. The vagina is self-cleaning; warm water externally is sufficient.

When to see a clinician

Get assessed if you notice any of the following lasting more than a few days: a persistent fishy or foul smell, a change in discharge colour or consistency, itching, soreness or burning, pain during sex or urination, or bleeding between periods.

If you have had a new sexual partner in the past three months, testing for STIs alongside BV and thrush is sensible even if your only symptom is a change in smell.

Our Silver Screen (£375 for women) covers chlamydia, gonorrhoea, mycoplasma, trichomoniasis, ureaplasma, Gardnerella, herpes, syphilis, HIV, plus a bacterial swab for candida and BV. This is the most appropriate package when vaginal odour is your primary concern, because it captures both STI and non-STI causes in one visit.

How we test

Walk-in testing is available seven days a week at our Harley Street clinic. No appointment or GP referral is needed. All samples are processed by UKAS-accredited laboratories.

You do not need to use your real name, and we accept cash payment.

For vaginal odour concerns, we typically recommend a combination of swab and blood testing. A swab screens for BV, thrush, trichomoniasis, and other vaginal infections. Blood tests cover syphilis, HIV, and herpes antibodies.

Results are available from 24 hours for blood samples and 1-3 days for swabs. If results are positive, our doctors can prescribe treatment the same day.

Frequently asked questions

Does chlamydia cause a smell?

Chlamydia can cause a mild change in vaginal odour in some women, but many women with chlamydia notice no smell at all. The absence of odour does not rule out chlamydia. A PCR test is the only reliable way to confirm or exclude it.

Why do I smell fishy after sex?

The most common cause is bacterial vaginosis. Semen is alkaline, which raises vaginal pH and releases amines that produce a fishy odour. This is a chemical reaction, not necessarily a sign of an STI. However, trichomoniasis can also produce a fishy smell that worsens after sex, so testing is worthwhile if the smell is persistent or new.

Can BV turn into an STI?

BV itself is not an STI and does not "become" one. However, BV disrupts the vaginal microbiome and increases susceptibility to STIs including chlamydia, gonorrhoea, and HIV. Treating BV promptly reduces this risk.

Should I wash more if I notice a smell?

No. Over-washing, douching, and using scented products are among the most common triggers for bacterial imbalance and worsening odour. The vagina does not need internal cleaning. Wash the external vulval area with warm water only. If odour persists, it needs clinical assessment, not more washing.

References

• BASHH (2024). UK National Guideline for the Management of Bacterial Vaginosis.
• BASHH (2024). UK National Guideline on the Management of Trichomonas vaginalis.
• NICE CKS (2024). Bacterial vaginosis — Diagnosis and management.
• NICE CKS (2024). Vaginal discharge — Assessment and causes.
• NHS (2024). Vaginal discharge.