Top 10 Symptoms of Mould Toxicity & How to Spot Them

As reported by the Herald Sun, in Victoria, a family in Geelong was forced to vacate their home just before Christmas due to a severe black mould infestation. Air testing revealed spore counts were 90 times higher than recommended safety levels, rendering thousands of dollars’ worth of their belongings unusable.

Mould toxicity in Australia isn’t just a minor inconvenience; it’s a serious public health concern and a hidden economic burden. With high rates of indoor mould, especially after floods or in homes with poor ventilation, health risks and structural damage can escalate rapidly. In many cases, residents and business owners underestimate the long-term impacts, which can lead to costly repairs and chronic health issues down the line. 

Before we explore the symptoms of mould toxicity, it’s essential to understand exactly what mould toxicity is and how it differs from simple mould exposure. 

What is Mould Toxicity? (And Why It Matters)

Mould is far more than just an unsightly patch on your walls or ceilings. Certain types of mould, especially species like Stachybotrys chartarum (commonly known as black mould), can release microscopic spores and mycotoxins into the air. When inhaled or ingested over time, these substances can trigger significant health problems. 

According to the World Health Organisation (WHO), damp and mouldy indoor environments are strongly associated with respiratory illnesses, allergic reactions, and the worsening of asthma. If you’d like to explore more about the different types of mould, how they spread, and answers to common homeowner questions, check out All About Mould: FAQs and Expert Answers. 

Important Note: It’s crucial to distinguish between simple mould exposure and mould toxicity. While many people might experience mild allergy-like symptoms from everyday mould exposure, mould toxicity refers to a more serious reaction to mycotoxins that accumulate in the body over time, potentially leading to neurological, respiratory, and immune system complications.

The Top 10 Symptoms of Mould Toxicity

Recognising mould toxicity symptoms early is key to preventing long-term health problems. Here are some expert-identified signs of mould toxicity that can help protect you and your family from more serious complications.

✅ Persistent Coughing & Wheezing

One of the most common signs of toxic mould in homes is respiratory distress. If you’re coughing, wheezing, or experiencing shortness of breath without another clear cause, mould could be lurking nearby.

✅ Headaches & Brain Fog

Long-term mould exposure is linked to neurological symptoms like frequent headaches, dizziness, and trouble concentrating. Some people describe it as a “mental haze” or feeling unusually forgetful.

✅ Itchy Eyes, Nose, or Throat

Mould allergens often cause irritation and inflammation of the mucous membranes. If your eyes water and itch frequently indoors, it could be more than just seasonal allergies.

✅ Unexplained Skin Rashes

Toxic mould exposure doesn’t always affect only the lungs. Prolonged exposure can cause redness, hives, or eczema-like rashes that may worsen over time.

✅ Chronic Fatigue

Living or working in a mould-infested space can wear your immune system down, leading to constant tiredness even after a full night’s sleep. This is a key symptom of long-term mould exposure. 

Important Tip: If multiple family members are feeling drained or sick at home but improve elsewhere, mould could be the culprit.

✅ Frequent Sinus Congestion

Mould spores irritate your nasal passages and sinuses. Chronic stuffiness, runny nose, or sinus pressure that doesn’t respond to usual allergy medication can indicate mould exposure.

✅ Heightened Allergies

If you notice seasonal allergies persisting year-round, especially indoors, mould may be thriving in hidden spots like under carpets, behind walls, or in your HVAC system.

✅ Muscle Aches & Joint Pain

Though less commonly linked, mycotoxins can sometimes cause inflammatory responses in the body, resulting in unexplained muscle stiffness or joint discomfort.

✅ Worsening Asthma or Breathing Disorders

Mould is a well-known asthma trigger. Those with asthma or COPD often find their conditions worsening when exposed to damp, mouldy air.

✅ Mood Changes & Anxiety

Emerging studies suggest that prolonged exposure to toxic mould may influence the nervous system, potentially leading to irritability, mood swings, or even depression.

How to Spot Toxic Mould in Your Home

Spotting the symptoms of mould toxicity is only half the battle. Simply knowing the signs of mould won’t prevent future health risks or property damage that you need to identify and tackle the source. 

First, locate where mould may be growing in your home. Once you find the spot, you can take steps to eliminate it and stop it from spreading.

Wondering whether it’s safe to tackle black mould yourself or better to hire experts? Our post on Black Mould Removal Methods: Professional vs. DIY breaks it down clearly.

• Look & sniff: Musty, earthy odours often signal mould, even if it’s hidden.
• Check damp areas: Bathrooms, kitchens, basements, and around windows are hotspots.
• Examine walls & ceilings: Discolouration, peeling paint, or bulging drywall may hide mould behind.

Pro Tip: Sometimes, mould hides inside HVAC ducts or under flooring. A professional inspection is often needed to detect concealed infestations.

What Should You Do if You Suspect Mould Toxicity?

Don’t ignore the signs. Long-term exposure increases health risks, especially for children, the elderly, or anyone with respiratory conditions. 

• Contact a certified mould inspector to assess your home.
• Use a dehumidifier to keep indoor humidity below 50%.
• Fix leaks promptly to prevent mould from thriving.
• If mould is found, hire professionals trained in safe mould removal to prevent spores from spreading. 

A June 2025 Guardian report on NSW flood survivors noted that winter floods trapped pervasive mould in homes and businesses, making it “almost impossible” to eliminate spores without professional intervention.

When to Seek Medical Help

If you or your family are experiencing persistent symptoms, consult your GP. They may recommend allergy testing or other evaluations to determine if mould is impacting your health. 

Final Thoughts

Understanding these top 10 symptoms of mould toxicity can help protect your health and property. The sooner you identify the problem, the easier it is to manage and safeguard your home and your well-being. 

Remember:

It’s not just about cleaning up visible mould. Address the moisture problem, and get professional help to ensure thorough remediation. 

Remember, fixing the source is just as important as removing the mould. Address the moisture problem and get professional help to ensure thorough remediation. For practical strategies you can start today, see our guide on Mould Reduction Tips to Prevent Mould Growth