What Mould Actually Does to Your Health
Mould is a biological organism that reproduces by releasing microscopic spores into the air. In a mould-affected home, these spores — along with microbial volatile organic compounds (MVOCs) released by actively growing mould colonies — become part of the air you breathe every time you’re inside.
The health effects of mould exposure are real, reasonably well-documented, and variable — they depend on the mould species, the concentration of spores and MVOCs in the air, the duration of exposure, and the individual’s sensitivity and health status.
This guide covers what the research says about mould health effects, which symptoms to look for, which individuals are most at risk, and when you should consider vacating your Northern Rivers home until remediation is complete.
Common Health Symptoms of Mould Exposure
Respiratory Symptoms
Mould spores are a well-documented respiratory irritant and allergen. The most common respiratory effects of indoor mould exposure include:
- Persistent cough — particularly a dry, irritating cough that worsens when in the affected property and improves when away
- Nasal congestion and runny nose — similar to hay fever, often worse in the morning or after time spent in affected rooms
- Sneezing — particularly when entering a mould-affected space or disturbing mould during cleaning
- Wheezing and shortness of breath — particularly in people with asthma or other respiratory conditions; mould is one of the most common asthma triggers
- Chest tightness — in more severe exposure situations or in sensitive individuals
Allergic Reactions
Mould allergies are common — it’s estimated that up to 10% of the population has some degree of sensitivity to common indoor mould species. Allergic reactions to mould exposure include:
- Sneezing and watery eyes
- Skin rashes or itching
- Nasal and throat irritation
- Allergic rhinitis symptoms
These reactions are typically immediate or near-immediate responses to mould spore exposure and are more likely in individuals who are already atopic (have hay fever, eczema, or food allergies).
Eye, Skin, and Throat Irritation
Direct or airborne contact with mould can cause:
- Irritated, red, or watery eyes
- Skin redness, itching, or rash (particularly from direct skin contact with mould)
- Sore or irritated throat
- Headache
Systemic Symptoms From Prolonged Exposure
In situations of significant sustained mould exposure — particularly in poorly ventilated spaces or where mould colonies are extensive — some individuals report:
- Fatigue — persistent tiredness that is worse after time spent in the affected property
- Headaches — often described as mild, persistent headaches that improve when away from home
- Cognitive effects — difficulty concentrating, brain fog (though the research on cognitive effects specifically attributable to mould is less clear)
- Sleep disruption — associated with respiratory irritation during the night
When Symptoms Suggest Mould: The Home Test
The single most useful indicator that your symptoms are mould-related (rather than from an unrelated cause) is whether they follow this pattern:
Symptoms are worse at home and improve when you’re away from home.
If you consistently feel better when you’re out of the house — at work, visiting friends, on holiday — and worse when you return, the indoor environment is a probable contributor. This pattern strongly suggests indoor air quality as a factor, with mould being one of the most common causes.
For families, notice whether different household members are affected differently. Children and adults who spend more time in a specific room — a home office, a bedroom adjacent to a bathroom with mould — may have more pronounced symptoms.
Who Is Most Vulnerable
Not everyone in a mould-affected home will have the same experience. Individuals most at risk of serious health effects from mould exposure include:
Children
Children spend more time indoors relative to their body weight, breathe more air relative to their body size, and have developing immune and respiratory systems. Sustained mould exposure in early childhood has been associated with increased risk of developing asthma and respiratory sensitisation.
In a mould-affected Northern Rivers home, children are typically the first to show symptoms — particularly respiratory symptoms like coughing and wheezing that may be attributed to recurrent colds or infections before mould is suspected.
People With Asthma
Mould is one of the most significant triggers for asthma exacerbations. Indoor mould exposure in an asthmatic individual can increase the frequency of symptoms, the severity of attacks, and the medication needed to control the condition.
If an asthmatic family member’s symptoms have worsened since moving into a property — or have become seasonally worse during the Northern Rivers wet season — indoor mould should be seriously considered as a contributing factor.
People With Respiratory Conditions
Chronic obstructive pulmonary disease (COPD), chronic sinusitis, allergic rhinitis, and other pre-existing respiratory conditions are exacerbated by mould exposure. The already-compromised respiratory system is less able to handle the additional irritant and inflammatory burden of mould spore inhalation.
Elderly People
Age-related changes in immune function and respiratory capacity reduce the body’s ability to manage the effects of mould exposure. Elderly residents of mould-affected Northern Rivers homes — particularly in Lismore, Casino, and Murwillumbah post-flood properties — are at higher health risk and should be prioritised for relocation if significant mould is identified.
People With Compromised Immune Systems
Individuals undergoing chemotherapy, organ transplant recipients, people with HIV/AIDS, and others with significantly suppressed immune function are at risk of more serious conditions from mould exposure — including invasive fungal infections from certain Aspergillus species. These individuals should not remain in any home with known significant mould until remediation is verified complete.
The “Black Mould” Question: Is Stachybotrys as Dangerous as People Say?
Stachybotrys chartarum — widely known as “black mould” or “toxic black mould” — has received enormous media attention and has developed a reputation that somewhat exceeds the scientific evidence.
What the evidence says:
Stachybotrys produces mycotoxins (satratoxins and other trichothecenes) that are toxic in laboratory settings. Whether typical indoor exposure to Stachybotrys produces mycotoxin levels sufficient to cause the most severe effects attributed to it in popular media (neurological damage, severe systemic effects) is contested in the medical literature.
What is clearly true:
- Stachybotrys does produce mycotoxins
- Stachybotrys grows on materials with high cellulose content (paper-faced drywall, timber) that have been wet for extended periods — exactly the conditions created by the 2022 Lismore floods and similar events
- Even if severe systemic effects from typical home exposure are overstated, the respiratory and allergenic effects of significant Stachybotrys growth are real
- Stachybotrys-contaminated material should be treated as a serious remediation priority
The practical bottom line: Any black mould in a Northern Rivers home should be professionally assessed. Don’t assume it is or isn’t Stachybotrys based on colour alone — many common mould species are dark. And don’t assume Stachybotrys is automatically catastrophically dangerous — but do take it seriously.
When Should You Consider Vacating?
Most households don’t need to vacate for mould remediation — surface mould treatment can often be done while the property is occupied (with appropriate precautions). But in some situations, temporary vacation is warranted:
Vacate immediately if:
- Any household member is experiencing severe respiratory symptoms, difficulty breathing, or systemic symptoms that improve immediately when they leave the home
- A medical professional has advised vacating the property due to mould
- Visible mould is extensive — covering multiple rooms or large surface areas
- The mould is Stachybotrys chartarum (or you suspect it might be) and there are children or immune-compromised individuals in the home
- The home is a post-flood property with significant concealed mould and active health symptoms in household members
Vacate during remediation work if:
- Full structural mould remediation is being conducted (containment zones, HEPA filtration equipment, material removal)
- Remediation involves Category 3 contaminated materials
Can remain at home if:
- Treatment is surface antimicrobial only, limited to a single bathroom or confined area
- There are no vulnerable household members (children, elderly, asthmatic, immunocompromised)
- The remediation area is well isolated from the living spaces
Frequently Asked Questions
Can mould make you sick even if you can’t see it? Yes. Mould in concealed locations — subfloor spaces, wall cavities, roof voids — releases spores and MVOCs into the living space above or below. Occupants can experience health effects from concealed mould that they cannot visually identify. In fact, some of the most significant health impacts from household mould come from concealed rather than visible mould, because visible mould tends to prompt action while concealed mould can go unaddressed for years.
How long does it take to recover once the mould is removed? Most people experience significant improvement in mould-related symptoms within a few days to weeks of mould removal and effective ventilation of the space. For people who have had severe, prolonged exposure, recovery may take longer. Some sensitised individuals remain reactive to lower mould levels than before — essentially, prolonged exposure can increase future sensitivity.
My doctor says my symptoms are probably not from mould. Who should I believe? Most general practitioners are not specifically trained in environmental health and indoor air quality. A GP may not consider mould as a cause of respiratory symptoms unless the patient specifically raises it. If you suspect indoor mould is affecting your health, request that the GP notes the temporal pattern of your symptoms (worse at home, better away), and consider requesting a specialist referral to an allergist or respiratory physician who can assess environmental sensitivity. In parallel, arrange a professional mould assessment of your home.
Is it safe to sleep in a bedroom with mould? This depends on the extent of the mould, its location relative to where you sleep, and your personal sensitivity. As a general principle, spending eight hours every night in a room with active mould — particularly ceiling or wall mould adjacent to where you sleep — provides sustained, concentrated exposure. If you are experiencing health symptoms and sleeping in a mould-affected room, consider temporary alternative sleeping arrangements while the mould is assessed and treated.
Get a Mould Assessment
If you or your household members are experiencing symptoms consistent with mould exposure, the first step is finding out whether significant mould is present in your Northern Rivers home.
Request a Free Quote — our assessment includes the information you need to make decisions about occupancy, treatment, and your family’s health.