Last updated: July 2026
Bathroom mould is a fungus that grows where moisture and poor ventilation combine. Shower grout, bath seals, ceiling corners, and curtain hems are the most common sites. NSW Health lists specific health effects for people who are sensitive to it, including nasal irritation, wheezing, and asthma attacks. Most people with brief exposure have no symptoms at all.
This guide covers what causes mould in bathrooms, who is at greatest risk, how to remove it using the cleaning solutions NSW Health recommends, and what to do when cleaning alone does not fix the problem.
What Causes Bathroom Mould
Mould needs moisture and nutrients to grow. Bathrooms provide all three: steam from hot showers raises humidity, water sits on grout and seals, and surfaces accumulate dust and soap residue. Poor ventilation prevents surfaces from drying between uses, which is what allows mould to establish rather than just settle.
NSW Health notes mould growth commonly occurs on bathroom tiles, walls, ceilings, carpets, and insulation material when moisture accumulates.
Common sites in a Sydney bathroom:
- Grout lines in the shower recess
- Ceiling corners where steam collects
- Bath seals and caulking around the tub
- The back face of shower curtains and beneath bath mats
- Around and behind the toilet
If mould returns quickly after cleaning, there is usually a structural moisture source: a dripping fitting, a cracked pipe behind tiles, or rising damp from poor sub-floor ventilation.
Health Risks of Bathroom Mould
NSW Health (2022) is direct on this: most people who encounter mould will not develop health problems. Everyone breathes in mould spores outdoors; brief indoor exposure rarely causes illness.
People who are already sensitive to mould face a higher risk. NSW Health identifies specific health effects:
- Runny or blocked nose
- Irritation of the eyes and skin
- Wheezing
- Asthma attacks (in people already diagnosed with asthma)
People with asthma, allergies, or other breathing conditions are more sensitive to mould than the general population. People with weakened immune systems (including those with HIV infection, people on chemotherapy, or organ transplant recipients) and those with chronic lung diseases such as COPD or emphysema face a higher risk of mould infection in the lungs.
In rare cases, prolonged heavy exposure can lead to hypersensitivity pneumonitis, a lung inflammation that produces flu-like symptoms including fever, cough, chills, and shortness of breath. NSW Health notes symptoms may worsen the longer exposure continues.
If you or a family member develops any symptoms after exposure to mould, see a GP. For a life-threatening emergency, call 000.
How to Prevent Bathroom Mould
The root cause is always moisture. Prevention means reducing how long surfaces stay wet.
Ventilation
NSW Health recommends turning on exhaust fans during bathing and showering. Running the fan for around 30 minutes after a shower allows residual steam to clear before surfaces cool and moisture settles. If there is no exhaust fan, opening a window after every shower improves cross-ventilation and helps surfaces dry.
Reducing surface moisture
- Use a squeegee on shower screens and tiles after each use; this removes the surface water mould needs before it evaporates
- Hang towels, bath mats, and shower curtains to dry fully between uses; wet fabric left bunched or rolled is a reliable mould site
- Dry the toilet cistern and tank surrounds, which collect condensation in cooler weather
Addressing structural moisture
A dripping fitting or leaking pipe behind tiles provides continuous moisture that no amount of cleaning eliminates. Repair all water leaks promptly. If water has entered your home, completely clean and dry any water-damaged materials; discard materials that cannot be fully dried.
Other prevention measures
- Repaint with a semigloss finish: water beads off rather than soaking into painted surfaces
- Maximise natural light by keeping blinds open when the bathroom is not in use; sunlight inhibits mould growth
- Open shower doors and curtains after use to allow airflow inside the recess
How to Remove Bathroom Mould
NSW Health recommends a two-stage approach depending on how established the mould is.
Stage 1: Routine mould on tile and glass surfaces
Mix 4 parts white vinegar to 1 part water. Spray onto affected surfaces, leave briefly, then scrub with a stiff-bristled brush. Use an old toothbrush for grout lines and caulking. Wipe clean, then dry the surface completely.
Stage 2: Stubborn mould that does not respond to vinegar
Diluted bleach is the alternative recommended by NSW Health for mould that will not come off with vinegar. Mix 250ml of bleach in 4 litres of water. Before using bleach:
- Make sure the area is well-ventilated (open windows, run the exhaust fan)
- Wear PVC or nitrate rubber gloves, safety glasses, and safety shoes
- Dry the surface completely after cleaning
After either cleaning method: mould will return if the moisture source is not addressed. Cleaning removes mould; fixing ventilation and leaks prevents it returning.
Grout that cannot be cleaned
Mould that has penetrated grout fully cannot be scrubbed out. The grout needs to be removed and replaced.
Absorbent materials
Bath mats, shower curtains, and soft furnishings that cannot be properly cleaned may need to be replaced rather than cleaned. NSW Health confirms absorbent materials such as carpet may need professional cleaning or replacement.
When to Call a Professional
Mould on tile and glass surfaces can generally be handled with the steps above. Contact a professional mould remediation service when:
- Mould is suspected inside wall cavities or the ceiling (NSW Health notes this may not be visible and may require specialist testing)
- You have found and cleaned visible mould but symptoms persist
- Mould returns within days of cleaning despite fixing ventilation (indicates a hidden moisture source)
If you cannot find the source of the problem, NSW Health recommends an occupational hygienist for specialist mould testing.
Renters in NSW: If you have properly ventilated the bathroom and mould persists, NSW Fair Trading advises raising the issue with your landlord or property manager. Contact NSW Fair Trading on 13 32 20.
Clearing out mouldy bathroom items? Mould sometimes permanently damages items beyond cleaning: mattresses, bathroom vanities, renovation offcuts. Paul's Rubbish Removal collects these from anywhere across Sydney, with same-day pick-up available when you book before 10am. Book a pick-up
Frequently Asked Questions
Why is a mushroom growing in my bathroom?
A mushroom in a bathroom signals a severe and persistent moisture problem. Mould is always present at low levels, but mushrooms (which are also fungi, per NSW Health) only produce visible fruiting bodies after extended periods of very high moisture, usually from a hidden water leak or serious structural damp behind tiles or under the floor. Remove the mushroom, then find the moisture source before cleaning the surface. Visible bathroom mushrooms are a sign to call a plumber or building consultant, not just a cleaning problem.
Is black mould in bathrooms more dangerous than regular mould?
NSW Health states that many types of mould exist and all have the potential to cause health problems, particularly for people with asthma, allergies, or weakened immune systems. The severity of any mould exposure depends on the extent of growth, ventilation, and individual sensitivity rather than colour alone. Treat all visible mould as a concern and remove it promptly.
Can vinegar permanently remove bathroom mould?
NSW Health recommends vinegar (4 parts to 1 part water) for routine mould removal from tile surfaces. For stubborn mould, diluted bleach (250ml in 4 litres of water, with proper PPE) is the alternative. Neither vinegar nor bleach prevents mould returning if the moisture source is not fixed. Ventilation and surface drying after each shower are what stop recurrence.
What do I do with mouldy bathroom items I cannot clean?
Absorbent materials such as bath mats, shower curtains, and upholstered items that cannot be cleaned properly may need to be replaced. For larger items, a rubbish removal service can collect and dispose of them.
