Are Domestic Moulds Harmful to Health

Are Domestic Moulds Harmful to Health

By Ruth MacEachern

Product Manager

Mould is more than just an unsightly nuisance lurking in the corners of our homes. For countless households across the UK, mould growth is a persistent and sometimes invisible threat that is made worse by condensation and damp conditions.

Although it is first noticed because of the stains it causes on walls and ceilings, certain mould species release spores and toxins that can seriously affect your health.

What is mould and why does it grow?

Mould is a type of fungus that thrives in damp, humid, and poorly ventilated environments. In the UK, where the climate is often wet and cold, mould can quickly become a problem, especially in homes where condensation collects and moisture is unable to escape. The key ingredients for mould growth are simple: moisture, warmth, and organic material to feed on—such as wallpaper, paint, wood, or even dust.

Condensation is often the root cause of mould

Condensation occurs when warm, moist air contacts a cold surface like a window or exterior wall which causes water droplets to form. Activities like cooking, showering, drying clothes indoors, and even breathing contribute to this build-up of moisture and if a home is poorly ventilated, this water vapour in the air cannot escape.

When high levels of humidity are not dealt with, condensation can quickly develop into damp patches which create the perfect place for mould to grow.

Common Mould Species in UK Homes

A variety of mould species can establish themselves in domestic settings, but some are more commonly encountered because of condensation and dampness.

Aspergillus appears as black, green, or grey patches and is often found on walls, ceilings, and even soft furnishings. Aspergillus is particularly widespread in bathrooms and kitchens and is the mould that is most often associated with condensation damp.

Penicillium is recognisable through its blue-green, velvety appearance, Penicillium consumes starches and as such, you will often see it growing on surfaces like wallpaper, carpet, and furniture. It is a fast-spreading mould when condensation is persistent.

Cladosporium is olive-green to black and is commonly found on damp windowsills, wooden frames, and in bathrooms.

Stachybotrys Chartarum (sometimes called “toxic black mould”) is usually dark green or black and forms slimy patches on wallpaper, plaster, and behind furniture positioned against exterior walls. Stachybotrys thrives in places that are chronically damp.

Toxic Black Mould releases harmful mycotoxins into the air, and if you suspect that this type of mould is present, you should have it professionally removed rather than exposing yourself to it by attempting to clean it without the proper equipment.

The health risks of exposure to mould

Mould releases microscopic spores and, in some cases, toxins called mycotoxins into the air. The health impact of mould in your home can depend on factors including the species, and individual sensitivity to allergens such as mould spores, as well as the amount of mould that is present. Common issues include respiratory problems such as coughing, wheezing and throat irritation.

Allergic reactions to mould such as sneezing and skin rashes are common, particularly among children and the elderly. The allergens from mould can also worsen conditions for people with an underlying illness such as asthma.

In rare cases, high concentrations of the mycotoxins moulds such as Stachybotrys Chartarum can lead to neurological symptoms along with headaches and fatigue.

Removing mould safely

If you discover mould in your home, it’s important to remove it safely and address the underlying cause to prevent its return. Areas less than 1 square meter in size can be cleaned with a mild detergent, dilute bleach, or a fungicide spray. If you want to avoid the use of harsh chemicals, bicarbonate of soda as a paste or lemon juice can be effective at killing mould.

When cleaning mould you should always wear gloves, a mask, and goggles to avoid contact with spores

Spray your cleaning agent onto the affected area and then leave it to work for up to 15 minutes before scrubbing the mould loose and wiping away with a cloth. Once clean, dry the area thoroughly and dispose of any cloths you have used in a sealed bag to avoid spreading the mould elsewhere in your home.

Persistent or large infestations: Seek advice from a qualified professional, as extensive mould can penetrate wall linings and insulation, requiring specialised treatment.

After cleaning, dry the area thoroughly and dispose of cleaning materials and any contaminated items in sealed bags.

Prevent condensation from leading to mould

While cleaning removes visible mould, preventing its return requires addressing the underlying moisture problem. The most effective strategy is to reduce condensation by improving ventilation:

Improved airflow in your home reduces humidity levels which reduces the presence of damp and takes away the environments where mould can thrive.

Use extractor fans in bathrooms and kitchens whenever you cook or bathe. Ensure these fans are vented to the outside and run them for at least 20 minutes after use to clear lingering steam.

You should also take steps to reduce activities that create large amounts of water vapour by dry clothes outdoors where possible and using pan lids when cooking on the hob.

Try and keep large items of furniture at least two inches away from cold exterior walls to allow air flow and prevent mould developing behind sofas, beds, or cupboards.

When Simple Solutions Aren’t Enough: Whole House PIV Systems

For homes where mould or condensation occurs away from obvious moisture sources Positive Input Ventilation (PIV) systems can provide a solution.

PIV units draw filtered air into the house through a central unit and disperse it gently throughout the house to force out moisture-laden air through natural ventilation points such as air bricks. This creates a drier indoor environment and significantly reduces condensation, thus limiting the opportunity for mould to take hold. PIV systems are particularly useful for properties where persistent damp patches appear in bedrooms, hallways, or loft spaces, rather than just bathrooms or kitchens.

Find out more

If you have discovered mould in your home and are worried about the potential health risks to you and your family, we can help. Enter your postcode below to find a ventilation specialist in your area and book a free home survey to identify the sources of condensation and find a way to stop them.