The simple idea (no memorising)
A healthy reproductive‑age vagina is kept slightly acidic by friendly Lactobacillus bacteria. Trouble comes in three flavours:
- Bacterial vaginosis (BV) — not really an "infection" but an imbalance (the friendly bacteria are crowded out). Little inflammation. Thin grey discharge + fishy smell.
- Trichomoniasis — a sexually transmitted protozoan (a tiny swimming organism). Frothy yellow‑green discharge, an inflamed vagina, and a classic "strawberry cervix."
- Thrush (candida) — a fungus. Thick, white, curd‑like discharge + intense itching.
The one table that solves most questions
| Feature | BV | Trichomoniasis | Thrush (Candida) |
|---|---|---|---|
| Nature | imbalance | STI (protozoan) | fungus |
| Discharge | thin, grey | frothy, yellow‑green | thick, white, curdy |
| Smell | fishy | unpleasant | not fishy |
| Itch | little | some | intense |
| Vaginal pH | > 4.5 | > 4.5 | < 4.5 (stays acidic) |
| Under the microscope | clue cells | swimming organisms | yeast / threads |
| Treat the partner? | usually no | yes | usually no |
The two fastest clues
- "Clue cells" + fishy smell (positive "whiff" test) + pH above 4.5 → BV. (Doctors confirm BV with the Amsel criteria — needing 3 of 4: thin discharge, pH > 4.5, clue cells, positive whiff test.)
- Curdy white + fierce itch + normal acidic pH → thrush.
The partner rule (a favourite)
- Trichomoniasis → treat the partner (it's sexually transmitted, reinfection is common).
- BV and thrush → usually no partner treatment.
Why it matters
Discharge is one of the commonest reasons women see a doctor, and colour alone is misleading. The skill is reading the whole fingerprint — smell, itch, pH and microscope — not guessing from one feature.
Quick check ✅
- Which of the three itches the most, and which has a fishy smell?
- Which one needs the partner treated too?
Remember this 🌟
Where we're going next → These lower infections can climb higher — with lasting consequences. Concept 27.