The classic picture of bacterial vaginosis is thin, greyish white discharge with a fishy smell that gets stronger after sex. Itching is usually not the main complaint. That is the pattern, and yet around half of women with bacterial vaginosis notice little or nothing.
What makes this topic awkward is that every symptom points two ways. They tell you something, and at the same time they rule out almost nothing. Here is what each signal does and does not mean.
Which symptoms belong to bacterial vaginosis?
The most described features are an increase in thin, uniform discharge, a greyish white colour, and a smell often described as fishy. That smell usually gets stronger after unprotected sex, because semen briefly changes the acidity. Pain and itching are usually not part of it.
| Symptom | What it may suggest | What it does not rule out |
|---|---|---|
| Fishy smell | Bacterial vaginosis, especially after sex | Trichomonas also causes a strong smell |
| Thin greyish white discharge | Bacterial vaginosis | Chlamydia and gonorrhoea often run without odd discharge |
| Heavy itching | Candida rather than bacterial vaginosis | Trichomonas can itch too |
| Burning when peeing | A bladder infection or irritation | Chlamydia, gonorrhoea and trichomonas do this as well |
| No complaints at all | Nothing | Around half of infections run silently |
Look at the right-hand column and the conclusion writes itself. Symptoms are a starting point, not an answer.
Why does it smell like fish?
Because of amines released when certain bacteria take over. In bacterial vaginosis the lactobacilli decrease, which makes the vagina less acidic. In that milder environment, species grow that produce compounds with that typical smell. Semen is mildly alkaline, so after sex the smell usually becomes clearer.
Amsel and colleagues turned this into a test in 1983: a drop of potassium hydroxide on some discharge sharpens the smell immediately. It is called the whiff test and is still in use.
Something we think matters: that smell says nothing about hygiene. Washing more often or more thoroughly usually makes it worse, because it rinses away the very lactobacilli that keep the environment acidic.
Can bacterial vaginosis clear up on its own?
Yes, that happens regularly. Bacterial vaginosis can disappear spontaneously when the lactobacilli recover. At the same time it often returns: Bradshaw and colleagues saw a large share of women develop complaints again within twelve months of a course of metronidazole.
That spontaneous clearing is exactly why self-care looks so convincing.
Say you buy a gel, use it for 7 days and the complaints settle. Was that the gel, or the natural course? From your sofa there is no way to tell. The Farmacotherapeutisch Kompas describes which agents are usual for bacterial vaginosis, and why they differ from what is given for a parasitic infection.
When does a test add something?
When there has been a risk moment. Bacterial vaginosis itself is not in an STI test, but the infections that resemble it are. Chlamydia, gonorrhoea and trichomonas sometimes cause exactly the same change in discharge, and those do not clear up by themselves.
A chlamydia, gonorrhoea and trichomonas test rules out all three in one go. Whatever is left after that, your GP assesses.
Take someone aged 31 with months of shifting complaints who has tried self-care three times. The fourth attempt yields the same information as the first three: none. One test yields something.
What your GP does
Your GP can look at the discharge, measure the acidity and send material to a lab if needed. The NHG describes in its standard on vaginal complaints how that assessment runs in Dutch practice. It is also where candida and bacterial vaginosis get separated.
If I had to leave you with one thing: the smell you are worrying about is, to a doctor, simply a finding and not a judgement.
If you would rather tick off the STI side first without a conversation, that can be done separately.
Read on in the overview of bacterial vaginosis, thrush or trichomonas, about the bacterium itself in is gardnerella an STI, and about the STI that resembles it most in trichomonas symptoms in women.
Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
References
- Amsel R, et al. Nonspecific vaginitis. Diagnostic criteria and microbial and epidemiologic associations. The American Journal of Medicine, 1983. PMID: 6600371
- Muzny CA, Schwebke JR. Pathogenesis of Bacterial Vaginosis: Discussion of Current Hypotheses. The Journal of Infectious Diseases, 2016. PMID: 27449868
- Bradshaw CS, et al. High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy. The Journal of Infectious Diseases, 2006. PMID: 16652274
- Peebles K, et al. High Global Burden and Costs of Bacterial Vaginosis: A Systematic Review and Meta-Analysis. Sexually Transmitted Diseases, 2019. PMID: 30624309
- NHG, standard on vaginal complaints (fluor vaginalis)
- Farmacotherapeutisch Kompas, agents for bacterial vaginosis and trichomoniasis
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