In theory, menstrual blood collected in a cup barely has any smell. Unlike pads, where blood oxidises on contact with air and sits exposed, the cup is a closed environment.
However, you may notice a particular smell when you remove it. Metal? Cheese? Fish? These odours are messages from your body. Here's how to decode them and, most importantly, how to get rid of them.
Table of contents
1- The Odour Decoder (Diagnosis table)
Before panicking, identify what you're smelling. Most odours are harmless.
| The Smell | The Cause | Verdict |
|---|---|---|
|
Metal / Iron (Fresh blood) |
Haemoglobin | ✅ Normal. Your blood is iron-rich. This is actually a good sign! |
|
Cheese / Yoghurt (Lactic smell) |
Lactobacilli | ✅ Normal. Your vaginal flora is thriving. These "good bacteria" are protecting you. |
|
Fish (Stale / Ammonia-like) |
Infection | ❌ Alert. Potential sign of Bacterial Vaginosis or Trichomoniasis. See a doctor. |
2- In-depth analysis: Iron, Lactobacilli or Infection?
The Metal smell (Iron)
Iron is an essential component of haemoglobin. A coppery smell simply means your blood is healthy. It can vary depending on your diet (red meat, lentils, spinach, seafood…).
The Cheese smell (Lactobacilli)
This may be surprising, but it's actually great news!
Your vagina is protected by friendly bacteria: Lactobacilli. These are lactic acid bacteria — the same family found in cheese and yoghurt.
If your cup smells of cheese, it means your flora is strong and has colonised the silicone. This is common after a few months of use, because unlike tampons, the
cup does not kill these beneficial bacteria.
The Fish smell (The warning sign)
Here, the alarm bells should ring. A fishy smell (often accompanied by grey or foamy discharge) is the clinical sign of a pH imbalance (which has become too alkaline).
- Bacterial Vaginosis: The bacterium Gardnerella vaginalis has taken over.
- Trichomoniasis: An STI caused by a parasite.
👉 Action: Do not reinsert your cup. See a doctor or midwife for appropriate treatment. Sterilise your cup in boiling water before using it again.
3- Tutorial: How to deodorise your cup (Recipes)
If your cup is healthy but a persistent smell has worked its way into the silicone, here's how to restore it.
Reminder: Luneale's medical-grade silicone is inert, but it can absorb odours if not cleaned thoroughly.
Boil your cup in a saucepan of water, adding ONE of the following ingredients (do not mix them):
- 1 tablespoon of food-grade bicarbonate of soda.
- OR a splash of white vinegar.
- OR the juice of half a lemon.
4- Prevention: The role of size and cleaning
Prevention is better than cure. Two tips to stop odours from coming back:
A. The cold water rinse
This is the golden rule. Always rinse your cup with COLD WATER first. Hot water "cooks" the blood and sets odours into the silicone.
B. Minimising air exposure (Choosing the right size)
Odour comes from blood oxidising on contact with air.
If you use a Size L but have a light flow (end of your period), your cup will be 10% blood and 90% air. This encourages oxidation and odours.
👉 Tip: If your flow decreases, switch to a Size S or empty your cup more often (every 4 hours instead of 6) to refresh the air inside. And remember: never more than 6 hours without emptying it!
In short: An iron or lactic smell is normal. A fishy smell calls for a doctor. For everything else, a good bicarbonate bath does the trick!
