Why mould in the home is bad for your health

Damp problems and mould in the home can impact your health. Find out everything from what causes mould and its effects to how to remove and prevent it.

Mould can grow on everything from walls and floors to clothes, shoes and cupboards. There are many different types of mould, but you might find it commonly looks like small fuzzy spots, a stain or a smudge. And it could be affecting more than just aesthetics. Here’s the lowdown on mould in your home, and how to reduce the risks to your health.

What causes mould?

Mould is a type of fungus. It’s perfectly natural and plays an important role in our ecosystem, speeding up the decomposition of organic materials outdoors, like fallen leaves and dead trees. 

Indoors, however, it’s not so welcome. Mould grows best in damp, poorly ventilated and wet areas – to get going, it needs a water source. Common water sources include roof or plumbing leaks, flood damage, rising damp, condensation or elevated humidity levels.

“Moulds can grow on almost any surface,” says Jeroen Douwes, Professor of Public Health and Director of the Centre for Public Health Research at Massey University, New Zealand. “Homes affected by water damage or leaks, rising damp, condensation on walls due to poor insulation and ventilation, and high humidity are very likely to be affected by indoor mould, unless leaks or indoor dampness problems are remedied promptly.”

How to detect mould in your home

You might smell mould before you see it. If you can smell that tell-tale mustiness, check the places in your home where there isn’t much air circulation. For instance, have a look behind furniture and paintings, in the attic or at the back of cupboards and wardrobes for signs of mould.

Indoor mould is often visible as a stain, smudge or discoloured patch on surface areas affected by condensation or leaks, but sometimes it's hidden within wall cavities. Other indications of damp problems may include water stains, condensation on the inside of windows, peeling or cracked paint, peeling wallpaper and puddles of water forming under or around the house.

How does mould in your home affect your health?

Mould reproduces by making tiny particles called spores. According to NSW Health, most people will not experience health problems from coming into contact with mould. However, if it’s left to spread, mould can cause health issues, especially for people who have existing respiratory issues or compromised immune systems. Always seek medical advice if you are concerned about the effects of mould.

“Spores are carried in the air and may cause health problems if inhaled by people who are sensitive or allergic to them,” says Prof Douwes.

Symptoms of a possible mould allergy include:

• a runny or blocked nose
• irritated eyes
• dry skin
• sneezing
• wheezing or a cough.

The main treatment for mould allergies, which are diagnosed by a skin prick test or an allergen test, is to minimise exposure to mould. Other treatments include oral antihistamines, nasal sprays or immunotherapy to reduce sensitivity.

People with pre-existing respiratory problems can also be sensitive to mould. According to Asthma Australia, when a person with asthma inhales mould spores, they’re at increased risk of an asthma flare-up. Also, people with weakened immune systems or chronic lung diseases are more at risk of health problems from coming into contact with mould.

Speak to your doctor if you have any concerns about how mould is affecting your health.

What are the different types of mould?

There are thousands of different species of mould. Among the most common types found in Australian homes are:

• Aspergillus, a green or grey mould commonly found on food and in aircon systems. Most people with healthy immune systems won’t be affected by breathing it in, although for people with weakened immune systems it can lead to an infection in the lungs or sinuses.
• Cladosporium, a green or brown mould with a suede-like texture, found on household items like carpet, fabrics, upholstery, timber furniture, food and uncleaned refrigerators. It’s considered to be the primary source of mould allergy.
• Stachybotrys (aka ‘black mould’), a dark green or black mould with a slimy texture. It grows in areas that are damp, wet or humid over a long period of time and can produce toxic spores.

Whatever the colour or type, if you have any mould in your home, you should remove it. 

How to get rid of mould at home

When removing mould from your home, Better Health Victoria advises that you open doors and windows to ensure good ventilation, and wear protective clothing like a shower cap, rubber gloves, P1 or P2 face mask (available from hardware stores) and goggles.

Don’t brush the mouldy area, as this can flick spores into the air. Also, for larger areas, avoid vacuuming mould unless your appliance has a good HEPA filter, which traps particles rather than recirculating them back into the air.

Instead, wipe away the mould from surfaces using a household detergent or white vinegar and a microfibre cloth, rinsing it regularly to prevent spreading the mould. If you’re using a store-bought specialist mould-removal cleaning product, always follow the instructions on the label. After cleaning, dry the area thoroughly by letting the air circulate.

It’s important to note that the best way to control mould is to identify the source of the moisture and fix it, otherwise the mould is likely to regrow. If large areas of regrowth occur, you might need to call in a mould removal professional.

Prevention is better than cure

The National Asthma Council Australia recommends taking the following steps to reduce your exposure to mould:

• Clean mould off walls, ceilings and other areas of your house by cleaning with naturally fermented white vinegar solution.
• Use high-efficiency air filters – these may be integrated in air-conditioning, ventilation systems or in standalone air purifiers.
• Make sure there’s enough natural ventilation in your home, including the use of extractor fans.
• Seal leaks in bathrooms and roofs.
• Clear overflowing gutters and under-floor vents.
• Remove indoor pot plants, as they promote mould growth.
• Thoroughly dry or remove wet carpets.
• Treat rising damp as soon as it’s detected, by fixing leaks and installing a damp-proof course at the base of the wall.
• Avoid the use of organic mulches and compost heaps in the garden.

Words by Charmaine Yabslet and Sara Mulcahy
Updated April 2022