THE ULTIMATE GUIDE TO MOULD

Courtney Dow
May 22
9 min read

Updated: May 27

If you’ve ever spotted mould growing on your bathroom ceiling, clothes in the cupboard, or your toddler’s soft toys and thought “Is this safe?” — you’re not alone. Mould is one of the most common questions I get asked about as a low-tox living educator, and for good reason. Exposure to indoor mould can affect everything from your home’s air quality to your family’s immune system. In this blog, we’ll cover the must-know facts about mould: what causes mould in Australian homes, how to clean it safely without harsh chemicals, when it’s better to throw mouldy items away, and how to prevent it from coming back. Whether you’re a homeowner, renter, or mum just trying to keep your family healthy, this is your go-to guide for managing mould the low-tox way — backed by research.

What you will find in this in-depth guide:

What causes mould
Health impacts of mould exposure
Mould prevention
Bonus tips for preventing mould
Mould treatment & removal
Proper low tox mould removal techniques
When to discard mould infested items
Cleaning Mould: A step-by-step guide
Product recommendations & discounts

Understanding What Causes Mould

Mould thrives when five conditions are met: moisture, poor airflow, darkness, organic material (like dust), and time. Of these, moisture is the most critical. High humidity, leaks, spills, or condensation on cold surfaces can all create breeding grounds. Everyday activities such as showering, cooking, or drying laundry indoors contribute significantly to indoor moisture.

Poor ventilation exacerbates the problem. Stagnant air allows humidity to linger and temperatures to drop in certain corners, causing condensation and encouraging mould growth. Darkness, such as inside cupboards or behind furniture, also contributes—UV light naturally inhibits mould.

Lastly, time is a key factor. A brief moisture event that dries quickly won’t usually cause problems. But if conditions persist—like a damp bathroom ceiling or a wall behind furniture that stays musty—mould will take hold.

By understanding and controlling these contributing factors, you create an environment that is far less hospitable to mould.

Health Impacts of Mould Exposure

The health effects of mould vary widely, depending on an individual’s sensitivity, the mould species involved, and the level of exposure. For many, exposure triggers allergic reactions such as sneezing, itchy eyes, nasal congestion, sore throat, and skin irritation. Those with asthma may experience exacerbated symptoms, including coughing, wheezing, or even asthma attacks.

In people with weakened immune systems—such as transplant patients, chemotherapy recipients, or those with chronic illnesses—exposure can lead to serious fungal infections. In rare cases, hypersensitivity pneumonitis, an immune reaction in the lungs, can occur from prolonged exposure.

More concerning are chronic or toxic reactions. Some moulds produce mycotoxins that can lead to persistent health problems in heavily contaminated spaces. Symptoms may include fatigue, cognitive impairment (“brain fog”), mood disturbances, memory issues, and even neurological symptoms like tremors or dizziness. Mycotoxins have also been linked to hormonal imbalances and immune suppression in some cases.

While not everyone will experience severe symptoms, research has consistently linked mouldy environments to increased rates of asthma, chronic respiratory issues, frequent colds, and even eczema flare-ups. If you or your family feel unwell at home but better when away, mould could be a contributing factor.

Mould Prevention: Long-Term Defence Strategies

Since mould spores are naturally present in the air, the key to prevention lies in denying them the moisture and conditions they need to grow. Moisture control and proper airflow are paramount.

Start by keeping indoor humidity below 50–60%. In humid climates or damp homes, use a dehumidifier or the “dry mode” on your air conditioner. A hygrometer is a handy tool for monitoring humidity levels. Watch for signs like condensation on windows or walls, which may indicate that humidity is too high. Remove condensation promptly and investigate its source.

Ventilation is just as important. Ensure exhaust fans are installed in bathrooms, laundries, and kitchens, and that they vent outside—not into the roof void. After showers or cooking, run the fans longer or open windows to disperse steam. In areas with poor airflow like cupboards or basements, consider using vented louvres, fans, or moisture-absorbing products like silica gel. Avoid overfilling wardrobes and keep furniture slightly spaced from walls to allow air to circulate.

Address moisture issues promptly. This includes fixing plumbing leaks, roof damage, and any form of water ingress. If flooding occurs, dry everything thoroughly within 24–48 hours. Rising damp is also a concern, especially in older homes. Ensure your property has an intact damp-proof course, functioning gutters, and drainage systems. Less obvious sources like unflued gas heaters, large aquariums, or too many indoor plants can also contribute to moisture levels.

Bonus Tips for Reducing Mould in the Home

Here are some extra, practical habits that can go a long way in keeping mould at bay—especially in areas like bathrooms, laundries, and around appliances where moisture tends to build up:

Wipe down wet bathroom surfaces (tiles, mirrors, glass, benchtops) with a squeegee or microfiber cloth after showers, especially on humid days.
Leave your bathroom exhaust fan running for at least 30 minutes after a shower to properly extract lingering humidity.
Open bathroom windows during or after showering when weather permits, to increase airflow and assist drying.
Dry the rubber seal and door of your front-loading washing machine after each use, and regularly wipe it with a cloth soaked in diluted tea tree oil or vinegar.
Leave the washing machine door ajar between loads to prevent trapped moisture and musty odours.
Remove wet clothes from the washer promptly and avoid letting them sit inside for long periods.
Keep wardrobe doors slightly ajar or use moisture absorbers in damp-prone areas to reduce stagnant air.
Service air conditioning units and split systems at least once a year to clean filters, remove internal mould, and ensure efficient drainage.
Regularly check and clean dehumidifier tanks and filters, as mould can grow inside if left stagnant.
Use a ceiling fan or portable fan in stuffy rooms to keep air moving and prevent moisture settling on surfaces.
Avoid drying clothes indoors unless using a well-ventilated space with exhaust or dehumidification.
Declutter and clean closed spaces regularly, as clutter traps dust and inhibits airflow—two things mould loves.

These small, proactive steps can dramatically reduce the conditions mould needs to thrive and help maintain a dry, healthy living environment year-round.

Mould Treatment: Safe Removal and Effective Practices

Before any cleaning begins, the number one priority is identifying and fixing the source of moisture. Mould will persist and return if the environment that allowed it to grow—such as leaks, high humidity, or water intrusion—remains unaddressed. Repair any roof leaks, plumbing drips, rising damp issues, or humidity problems as your first step.

On hard, non-porous surfaces, the cleaning process should begin by vacuuming the area with a HEPA-filter vacuum. These vacuums are designed to trap microscopic spores, preventing them from becoming airborne—something that regular vacuums are not capable of. After vacuuming, gently wipe surfaces with a damp microfiber cloth. Microfiber is far more effective than cotton at capturing spores due to its fine weave. Always avoid dry scrubbing, as this can release mould spores into the air and exacerbate the problem.

Non-porous surfaces, such as glass, metal, glazed ceramic tiles, and sealed benchtops, are much easier to clean effectively because mould is unable to penetrate them. Instead, it sits on the surface, where it can be physically removed with the right tools and cleaning solutions. These surfaces can be safely cleaned using vinegar, detergent, or a mould-specific cleaner.

If mould is present on porous surfaces like carpets, fabric, unsealed wood, or plasterboard, cleaning the surface alone isn’t enough. Mould can root deeply into these materials, leaving behind invisible spores and toxic compounds (mycotoxins) even after cleaning. Severely affected porous items should either be professionally remediated or safely disposed of.

Ultraviolet (UV-C) light can be used as a supplemental treatment to reduce surface mould and degrade mycotoxins.

Natural sunlight can also help—placing rugs or cushions outside on a sunny day may reduce surface mould. However, while UV light may kill spores, it doesn’t remove them, and dead spores can still cause allergic reactions. Therefore, UV should always be used in conjunction with thorough physical cleaning.

Mould Cleaning: Proper Techniques and Low-Tox Solutions

One of the biggest myths around mould cleaning is the use of bleach. While bleach might make mould stains disappear temporarily, it doesn’t penetrate porous surfaces or destroy mould roots. Worse, the water in bleach can soak into materials like wood and plasterboard, potentially feeding the mould instead of killing it. Furthermore, bleach is a strong respiratory and skin irritant and produces harmful fumes, especially when mixed with other cleaners. For these reasons, health authorities including the EPA, CDC, and Australian health agencies discourage its use for routine mould treatment.

Instead, vinegar is a far more effective and low-tox option. Plain white vinegar—used either undiluted or at a 4:1 vinegar-to-water ratio—has been shown to kill around 80% of common mould species. It also penetrates porous surfaces better than bleach. For an added antifungal boost and a pleasant scent, you can add a few drops of clove oil or tea tree oil, both of which have natural mould-fighting properties. Essential oil blends like doTERRA’s On Guard also include clove and can be used similarly.

It is important to note, however, that even the best natural remedies cannot reach or eliminate mould that has taken root within porous materials. Once mould has begun to grow hyphae (thread-like roots) deep into fabrics, cushions, drywall, or untreated timber, surface cleaning with vinegar or essential oils will not remove the problem completely—nor will it neutralise the microscopic toxins (mycotoxins) that mould can leave behind. Even if the surface looks cleaner, these deeper residues can continue to affect indoor air quality and trigger health symptoms. That’s why vinegar and oils are best used as part of a broader strategy: they can clean and inhibit surface mould effectively on non-porous or lightly affected surfaces, but should not be relied upon to remediate mould that has colonised porous materials. In such cases, physical removal—either by discarding the item or engaging professional remediation—is the safest and most thorough solution

Mould can begin to take root in as little as 24 to 48 hours under the right conditions—namely, moisture, warmth, still air, and an organic surface to grow on.

Here’s what happens during that critical window:

Within 24 hours: Mould spores (which are already present in the air) can land on a damp surface and begin to germinate.
24–48 hours: The spores start to form hyphae—tiny root-like structures that penetrate into porous materials like fabric, wood, plasterboard, and carpet. At this stage, it becomes increasingly difficult to clean mould away with surface methods alone.
After 72 hours: Colonies are typically visible to the eye and may begin producing mycotoxins, which can affect indoor air quality and health.

Regardless of which cleaner you use, technique is everything. Always wear gloves, a respirator (P2/N95), and eye protection. Use the “wipe and fold” method: wipe a small area with a microfiber cloth, then fold the cloth to a clean side before wiping again. This reduces the chance of spreading mould across the surface. Never dip a used cloth into your clean solution—use a separate rinse bucket or disposable cloths. Keep surfaces lightly misted during cleaning to suppress spores and avoid dry scrubbing, which can send spores airborne. HEPA vacuums should be used before and after cleaning to reduce residual spores in the environment.

When to Discard Mould-Infested Items

One of the most challenging decisions during mould remediation is knowing when to let go of contaminated belongings. Porous materials like fabric, paper, insulation, and unsealed wood are particularly problematic. Once mould has penetrated, it’s nearly impossible to remove fully.

Drywall, ceiling tiles, and insulation should always be removed and replaced if mouldy.
Carpets and underlays that are damp or smell musty—even if mould isn’t visible—are typically not salvageable.
Upholstered furniture, cushions, and mattresses are extremely difficult to decontaminate. Unless affected only on the surface and cleaned immediately, these items should be discarded.
Clothing and bedding can be washed on hot cycles with vinegar or borax, but if the smell lingers or stains remain, disposal is safest.
Paper-based items like books or artwork should be professionally restored only if highly valuable; otherwise, they should be discarded.
As for furniture, varnished solid wood may be cleanable if mould hasn’t soaked in, while particleboard and MDF furniture often cannot be saved due to their porous nature and glue content.

If you’re unsure, the rule is simple: when in doubt, throw it out. No possession is worth risking your health.

Cleaning Mould Safely: A Step-by-Step Guide

Mould cleanup can release high levels of spores into the air, so safety is essential. Begin by donning appropriate personal protective equipment: long gloves, a P2 or N95 respirator, goggles or a face shield, and protective clothing.
Keep children, pets, and anyone with asthma or compromised immunity out of the area.
Next, isolate the cleaning zone. Close interior doors and, if possible, tape plastic sheeting over doorways and vents to contain airborne spores. Ventilate to the outside by opening a window and pointing a fan outward. Lay plastic or old sheets beneath the mouldy area to catch debris.
HEPA vacuuming before and after cleaning helps capture spores.
Start by lightly misting the mould with a spray bottle of water or diluted detergent. Never begin with dry brushing or scrubbing.
Apply your cleaning solution—vinegar, clove oil in water, or a non-toxic mould cleaner—and work in small sections. Using a microfiber cloth, gently wipe the surface, folding to a clean side for each wipe and changing cloths frequently to avoid spreading spores. Never reuse dirty cloths in your clean solution.
Once visible mould is removed, dry the area thoroughly using towels, fans, and a dehumidifier. Proper drying is crucial—any lingering moisture invites regrowth. After cleaning, dispose of used PPE, cloths, and drop sheets safely. Wash worn clothes in hot water, and consider showering to rinse off spores. Finish by vacuuming the room again with a HEPA vacuum.
If mould is extensive, located inside walls or ducts, or if you feel uncertain, consult a professional remediation service.