Mould and your health
A musty smell, black spots on the bathroom ceiling, a cough that won't settle. Damp and mould are common, especially in rentals, and they really can affect your breathing. Here's who is most at risk, how to clean up safely, and which tests are worth your money (spoiler: very few).
Quick answer: Damp and mould can cause a blocked or runny nose, cough, wheeze, more chest infections and asthma flares. A few people get rarer, serious lung problems. The fix is to stop the moisture, clean or remove the mould, and see your GP if you have symptoms. Testing your home or your urine for mould is usually not useful.
Who is most at risk
- People with asthma, allergies or other breathing conditions.
- People with a weakened immune system (for example during chemotherapy or after a transplant) or chronic lung disease: mould can cause infections.
- Babies and young children with wheeze.
- People who work with mouldy hay, grain or compost.
Symptoms
- Blocked or runny nose, sneezing, itchy or watery eyes, skin irritation.
- Cough, wheeze, a tight chest, or asthma that's harder to control.
- More frequent chest infections.
- Rare: fever, aches, breathlessness and cough that keep coming back after exposure, from an inflammation of the lungs called hypersensitivity pneumonitis.
Cleaning up safely
- Fix the water first. Mould comes back if the leak, condensation or poor ventilation isn't fixed. Dry wet things within 24–48 hours.
- Small areas (less than about 1 square metre) you can usually clean yourself. Bigger areas, hidden mould or flood damage: get a professional.
- Protect yourself: rubber or nitrile gloves, eye protection and a P2 or N95 mask. People with asthma or weak immunity should let someone else do it.
- Clean with detergent and water, or a vinegar solution (NSW Health: 4 parts vinegar to 1 part water).
- Bleach only for stubborn mould on hard surfaces: NSW Health suggests 250 mL of bleach in 4 litres of water. Ventilate well. Never mix bleach with ammonia or other cleaners: it makes toxic fumes.
- Throw out soaked porous items you can't clean and dry, such as ceiling tiles or carpet underlay.
- Prevent: use exhaust fans, open windows when you can, avoid drying clothes indoors without airflow, and keep humidity below 60% (ideally 30–50%). A cheap hygrometer measures it.
Renting? In general, landlords must keep rentals in reasonable repair. Report damp and mould in writing, keep photos, and contact your local tenancy authority if it isn't fixed. Rules vary by state and country.
What tests do and don't show
- Useful (from your GP): breathing tests for asthma, and allergy tests (blood or skin prick) for mould allergy. Specialists use other tests for rare lung conditions.
- Not useful: urine mycotoxin tests. They aren't approved for diagnosing illness. Healthy people have mycotoxins in their urine too, and no level has been shown to predict disease.
- Not useful: mould IgG tests for allergy, or blood "biotoxin" panels.
- Home mould testing is usually unnecessary. If you can see it, remove it. The species doesn't change the advice.
- "CIRS" or "mould illness": Australian health authorities say it is not a recognised disease and has no validated diagnostic criteria. If you're unwell, that doesn't mean your symptoms aren't real: it means the label and its tests aren't proven. Your GP can help look for causes that can be treated.
When to see a doctor
- Cough, wheeze or breathlessness that doesn't settle, or asthma that's getting harder to control
- Fever, cough and breathlessness that keep returning after time in a particular building
- You have a weakened immune system and develop a fever or new cough
- A baby or young child with wheeze
- Ongoing tiredness, brain fog or pain, whatever you think the cause is
Call 000 (or your local emergency number) for severe breathlessness, blue lips, or an asthma attack that isn't easing with your reliever.
Common questions
Can mould in my house make me sick?
Damp and mould are linked with a blocked or runny nose, cough, wheeze, more chest infections and asthma flares. Rarely, mould causes a serious lung inflammation called hypersensitivity pneumonitis, and people with very weak immune systems can get mould infections.
Is black mould toxic?
Any mould growing indoors should be cleaned up, whatever its colour or type. Some moulds can make toxins, but there is no good evidence that breathing them at the levels found in homes causes body-wide poisoning.
Should I get a urine test for mould toxins?
No. Urine mycotoxin tests aren't validated for diagnosing illness. Mycotoxins are found in the urine of healthy people, and no level has been shown to predict disease.
How do I clean mould safely?
Fix the water problem first. For small areas, wear gloves, eye protection and a P2 or N95 mask, clean with detergent or diluted vinegar, use diluted bleach only for stubborn mould on hard surfaces, never mix bleach with ammonia or other cleaners, and dry the area completely.
Do I need to test my home for mould?
Usually not. If you can see or smell mould, the advice is the same whatever the type: find the moisture, fix it and clean it up. Testing may help find hidden damp when you can't find the source.
For health professionals: the evidence, the CIRS debate, trials and guidelines are in our mould deep dive.
Evidence and more information
- NSW Health: Mould
- US EPA: A brief guide to mold, moisture and your home
- CDC: Tips on cleaning mould after a flood
- CDC MMWR: Unvalidated urine mycotoxin tests (2015)
- Australian Government: Biotoxins (indoor damp and mould) clinical pathway
- National Academies: Damp indoor spaces and health (2004)
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