Symptoms of Mould Exposure

Mould exposure affects millions of people each year, yet many struggle to recognise the warning signs. Whether you’re dealing with a persistent cough that won’t quit or unexplained fatigue, understanding the health effects of mould in your home or workplace is the first step toward feeling better.

Quick overview: common symptoms of mould exposure

If you’ve been exposed to mold, your body will likely let you know. The common symptoms of mould exposure typically affect the respiratory system first, but can extend to other areas depending on how long and how heavily you’ve been exposed.

Early warning signs include:

• Sneezing and runny or stuffy nose

• Dry or productive cough

• Wheezing or whistling when breathing

• Itchy, watery, or red eyes

• Sore or scratchy throat

• Skin rashes or itchy skin

• Recurring headaches

• Unexplained fatigue and low energy

Symptoms requiring urgent medical attention:

• Difficulty breathing or severe shortness of breath

• Chest tightness or chest pain

• Coughing up blood

• High fever with respiratory symptoms

• Confusion or altered mental state

The severity of your symptoms depends on several factors: how much mould you’ve been exposed to, how long the exposure has lasted, and your individual health profile. People with asthma, existing allergies, or a compromised immune system typically experience more intense reactions.

As a general rule, mild symptoms resemble hay fever type symptoms and usually resolve when you leave the mouldy environment. Moderate symptoms persist longer and may require medical treatment. Severe symptoms indicate significant exposure or underlying vulnerability and need prompt professional care.

What is mould and how does exposure happen?

Mould is a type of fungus that reproduces by releasing microscopic mold spores into the air. These spores float through indoor and outdoor environments, and when they land on damp surfaces, mold grows and spreads. Common molds found indoors include Aspergillus, Penicillium, Cladosporium, and the often-discussed black mold (Stachybotrys chartarum).

Mould thrives wherever there’s excessive moisture combined with organic material. This means your home provides plenty of opportunities for mold growth if conditions are right.

Common indoor mould hot spots:

• Bathroom tiles, grout, and shower curtains

• Basement walls, especially in older homes without proper ventilation

• Window frames and sills with condensation buildup

• Water-damaged drywall after leaks or floods

• Carpets and rugs in damp areas

• Behind wallpaper or panelling

• Ceiling tiles in rooms with roof leaks

• Around air conditioner units and condensation coils

Exposure to mold happens primarily through breathing in airborne spores and fragments. However, you can also experience allergic responses through direct skin contact with contaminated materials or by eating visibly mouldy food.

In temperate climates, outdoor mold counts peak during late summer and autumn when decaying vegetation releases spores. In humid or coastal regions, mould can be a year-round problem both indoors and outdoors.

One important clarification: the colour of mould—whether black, green, white, or orange—doesn’t by itself indicate how dangerous it is. The Environmental Protection Agency and disease control authorities recommend treating all visible mold growth seriously, regardless of colour.

Respiratory and sinus symptoms of mould exposure

The airways and sinuses bear the brunt of mould exposure because mold spores enter your body primarily through inhalation. Your respiratory system essentially acts as the first line of defence, which is why these symptoms often appear earliest and most prominently.

Upper respiratory symptoms:

• Frequent sneezing

• Runny or blocked nose

• Postnasal drip

• Sinus pressure and facial pain

• Sore or scratchy throat

• Constant need to clear your throat

• Throat irritation that doesn’t respond to typical remedies

Lower respiratory symptoms:

• Persistent dry or productive cough

• Wheezing or whistling sounds when breathing

• Chest tightness, especially when inhaling deeply

• Shortness of breath during normal activities

• Worsening of existing asthma or chronic lung disease symptoms

• Increased reliance on rescue inhalers

How do you distinguish mould-related respiratory issues from an ordinary cold or seasonal allergies? Look for these patterns:

Your symptoms worsen in a specific room or building and improve when you’re away. They persist beyond the typical 7-10 day duration of a viral infection—often continuing for 3-4 weeks or longer. You notice a correlation between time spent in damp environments and symptom severity.

Long-term exposure in susceptible individuals can contribute to chronic sinusitis, recurrent bronchitis-like illnesses, and progressive decline in respiratory function. If you’re experiencing nasal congestion that simply won’t resolve, mould in your environment may be a contributing factor worth investigating.

Allergic reactions and mould-related asthma

A mold allergy works similarly to pollen or dust mite allergy—it’s an IgE-mediated immune response where your body overreacts to something that isn’t inherently harmful. When someone with a mold allergy breathes in spores, their immune system recognises them as invaders and releases histamine and other inflammatory chemicals. This inflammatory reaction happens within seconds to minutes of exposure.

Typical allergy symptoms include:

• Itchy nose with frequent sneezing

• Itchy, red, or irritated eyes

• Runny nose (allergic rhinitis)

• Watery eyes and eye irritation

• Itchy skin, hives, or skin rash after contact

• General feeling of “stuffiness” in the head

The overlap between allergy symptoms and asthma symptoms is significant. Many people with mold allergy also have asthma, and mould exposure can trigger or worsen both conditions simultaneously. This dual response creates a compounding effect where upper respiratory allergy symptoms combine with lower airway constriction.

Signs that mould is triggering asthma:

• Episodes of wheezing that correlate with being in specific locations

• Tight chest sensation, especially at night

• Night-time coughing that disrupts sleep

• Needing to use your rescue inhaler more frequently than usual

• Asthma attacks triggered by entering basements, older offices, or bathrooms without proper exhaust fans

Some people only notice problems in specific damp, musty spaces. If your symptoms flare in one particular building but not others, that’s a strong indicator of localised mold issues affecting your indoor air quality.

In rare but more serious cases, significant mould exposure can lead to conditions like hypersensitivity pneumonitis (an inflammatory response deep in the lungs) or allergic bronchopulmonary aspergillosis (ABPA), particularly in people with occupational exposure such as farmers, construction workers, or those working in mouldy buildings. These conditions require specialist evaluation and treatment.

For ongoing allergy management, some individuals benefit from allergy shots (immunotherapy), though effectiveness varies. Consulting with an allergy foundation or environmental medicine specialist can help determine the best approach for your situation.

Neurological, cognitive, and mood symptoms

Beyond the respiratory system, some people report “whole-body” symptoms with prolonged mould exposure, particularly effects on the brain and nervous system. The mechanisms behind these symptoms are still being actively researched, with mycotoxins—toxic compounds produced by certain moulds—suspected as a primary cause of mold toxicity affecting the nervous system.

Mycotoxins can trigger inflammation in the brain and irritate the central nervous system. This may explain why some people exposed to mold experience symptoms that extend far beyond typical allergy presentations.

Commonly reported neurological and cognitive complaints:

• Brain fog and difficulty thinking clearly

• Slower mental processing speed

• Trouble concentrating at work or school

• Short-term memory problems

• Morning headaches that improve after leaving home

• Migraines that worsen in mouldy environments

• Tingling or numbness in hands and feet

• Cognitive difficulties that interfere with daily tasks

Mood-related changes linked to chronic exposure:

• Increased irritability and short temper

• Heightened anxiety without clear cause

• Low mood or symptoms resembling depression

• Mood swings that seem disproportionate to circumstances

• Reduced tolerance for stress

• Poor sleep quality or insomnia

• Feeling “wired but tired”

These symptoms are notably non-specific—stress, viral infections, hormonal changes, and many other factors can produce similar effects. Mould should be considered as one possible contributor rather than automatically assumed to be the sole explanation. However, if these symptoms appeared or worsened after moving to a new home, starting work in a different building, or following water damage, the connection is worth exploring.

People with existing neurological or mental health conditions may find their baseline symptoms worsen when living or working in a damp, moldy environment. The added inflammatory burden can tip a manageable condition into something more difficult to control.

Skin, eye, and digestive symptoms

While the airways receive most of the attention in discussions of mould exposure, your eyes, skin, and digestive system can also react to mould and its byproducts. These symptoms often accompany respiratory issues but can sometimes appear independently.

Eye symptoms:

• Red, itchy, or burning eyes

• Excessive watering or tearing

• Gritty “sand in the eye” sensation

• Increased discomfort when wearing contact lenses in mouldy spaces

• Persistent eye irritation that doesn’t respond to typical eye drops

Skin symptoms:

• Itchy rash or hives after exposure

• Dry, scaly patches on exposed skin

• Worsening eczema or dermatitis

• Reactions after touching mouldy surfaces, fabrics, or porous materials

• Skin irritation concentrated on hands and arms (contact areas)

Using rubber gloves when cleaning potentially mouldy areas can help prevent direct skin contact and reduce these reactions.

Digestive complaints:

• Nausea, particularly after time in mouldy spaces

• Abdominal pain or cramping

• Bloating and gas

• Diarrhoea or irregular bowel movements

• Decreased appetite

Digestive symptoms most commonly occur after ingesting mouldy or mycotoxin-contaminated foods. Serious gut illness from environmental mould in homes is less common than respiratory effects, but low-grade digestive symptoms may coexist with other signs of exposure. Some research suggests mycotoxins can disrupt the gut microbiome, potentially contributing to ongoing digestive sensitivity.

Who is most at risk from mould exposure?

Anyone can experience irritation from high levels of mould, but certain groups face significantly greater health risks. For these vulnerable populations, what might cause mild symptoms in a healthy adult could lead to serious illness.

High-risk groups include:

• People with asthma or existing respiratory conditions

• Individuals with chronic lung disease such as COPD or cystic fibrosis

• Those with known mould allergies or environmental sensitivities

• Young children, whose immune systems are still developing

• Adults over 65, who may have reduced immune function

• Pregnant women

• People with weakened immune systems, including:

  • Cancer patients undergoing chemotherapy

  • Organ transplant recipients on immunosuppressive medications

  • Individuals on long-term corticosteroid therapy

  • People living with HIV/AIDS

Workers with occupational exposure:

• Construction and remediation workers handling contaminated materials

• Farmers regularly exposed to hay, grain, and compost

• Staff in archives, libraries, or museums with water damage

• Employees in older, poorly ventilated buildings

• Healthcare workers in flood-affected facilities

For these groups, mould exposure can lead beyond typical allergy and irritation to actual fungal infections of the lungs, sinuses, or skin. A person with a severely weakened immune system might develop invasive aspergillosis—a serious condition requiring aggressive medical treatment.

Interestingly, pets can also show signs of mould exposure. If your dog or cat develops unexplained coughing, sneezing, scratching, or skin irritation, it may be worth investigating your home for mold issues. Animals often spend more time at floor level where spore concentrations can be higher.

Short-term vs long-term health effects of mould exposure

The health consequences of mould exposure differ significantly depending on whether you’re dealing with a brief encounter or ongoing chronic exposure over months or years. Understanding this distinction helps you gauge the urgency of addressing mould in your environment.

Short-term exposure effects:

• Transient allergy-like symptoms that resolve quickly

• Temporary cough or throat irritation

• Mild headaches while in the moldy environment

• Sneezing and runny nose that clears within hours

• Symptoms improve within days after leaving the affected area

• Generally no lasting health consequences in healthy individuals

Long-term exposure effects (months to years):

• Chronic nasal congestion that becomes your “new normal”

• Recurrent sinusitis requiring repeated antibiotic courses

• Persistent cough that doesn’t fully resolve

• Progressive worsening of asthma symptoms

• Chronic fatigue and reduced stamina

• Ongoing cognitive complaints and brain fog

• Increased susceptibility to respiratory infections

• Development of new sensitivities to chemicals and fragrances

• In severe cases, pulmonary fibrosis (scarring of lung tissue)

For severely immunocompromised individuals, chronic exposure may contribute to serious fungal infections such as aspergillosis. These conditions require specialist care and can be life-threatening if not treated promptly.

The key message: long-term mould problems in a home or workplace should be treated as both a building issue and a health issue. Poor ventilation, ongoing water leaks, and unaddressed dampness aren’t just cosmetic problems—they represent ongoing health hazards that worsen with time.

When to see a doctor and what to tell them

If you’re experiencing persistent or worsening symptoms that might be linked to mould, don’t dismiss them as “just allergies.” This is especially important if you’re having breathing difficulties or belong to a high-risk group.

Red-flag symptoms requiring prompt medical review:

• Difficulty breathing or rapidly worsening shortness of breath

• Chest pain or severe chest tightness

• Coughing up blood

• High fever combined with respiratory symptoms

• Confusion or altered mental state

• Symptoms in someone with a very weakened immune system

• Severe allergic reactions including facial swelling

What information helps your healthcare professional:

• When your symptoms started and how they’ve progressed

• Where symptoms are worse (home, work, school) and where they improve

• Presence of visible mold or musty smells in your environment

• History of water leaks, flooding, or dampness in your building

• Previous diagnoses of allergies, asthma, or respiratory conditions

• Any recent changes in your living or working environment

• Whether family members or coworkers have similar symptoms

Possible diagnostic steps your doctor may use:

• Physical examination including lung auscultation

• Lung function tests (spirometry)

• Allergy skin prick tests or blood tests for specific mould antibodies

• Chest X-ray or CT scan in more serious cases

• Sputum cultures if fungal infection is suspected

• Referral to an allergist or pulmonologist for complex cases

Seek emergency care immediately if breathing is rapidly worsening or if a child, elderly person, or immunocompromised individual becomes suddenly very unwell after being in a moldy environment. Don’t wait to “see if it gets better.”

Professional mold testing of your home can provide objective evidence to share with your doctor and help establish the connection between your environment and symptoms.

Reducing symptoms by tackling mould in your environment

Lasting symptom relief usually requires a two-pronged approach: medical treatment for your current symptoms and practical steps to reduce mould exposure at its mold source. One without the other often leads to recurring problems.

Fix moisture problems promptly:

• Repair roof and plumbing water leaks within 24-48 hours

• Dry wet areas immediately after spills or minor flooding

• Address condensation on windows and pipes

• Promote groundwater drainage away from your building’s foundation

• Fix any issues that allow excessive moisture to accumulate

Control indoor humidity:

• Keep indoor humidity levels below 50% (ideally 30-50%)

• Use dehumidifiers in basements, bathrooms, and other damp areas

• Run exhaust fans in bathrooms and kitchens, vented to outdoors

• Ensure your central air conditioning system is properly maintained

• Clean condensation coils and drip pans on air conditioner units regularly

• Consider mold inhibitors in paints for high-moisture rooms

Improve ventilation:

• Use exhaust fans during and after showers and cooking

• Open windows regularly when weather and outdoor air quality allow fresh air circulation

• Ensure proper ventilation in attics and crawl spaces

• Don’t block air vents with furniture or storage

Clean and remove mould:

• Clean small areas of mould on hard surfaces using mold killing products

• Wear rubber gloves and an N95 mask when cleaning mould

• Remove and safely dispose of heavily mouldy porous materials (ceiling tiles, drywall, carpets)

• Don’t simply paint over visible mold—it will return

Filter and purify indoor air:

• Use high efficiency particulate air (HEPA) filters in your HVAC system

• Consider air purifiers with HEPA filters in bedrooms and living spaces

• Replace filters regularly to trap mold spores effectively

• Vacuum with HEPA-equipped vacuums to reduce settled spores

Know when to call professionals:

• Extensive mould covering more than 10 square feet

• Hidden mould inside walls or HVAC systems

• Mould resulting from sewage or contaminated water

• Situations following major flooding

• When symptoms persist despite DIY cleaning efforts

Simply covering up mould with paint or air fresheners doesn’t solve the problem—it allows the issue to worsen while masking the warning signs. Professional remediation may be necessary for significant contamination.

Key takeaways

• Mould exposure symptoms range from mild (sneezing, runny nose, itchy eyes) to severe (breathing difficulties, chest pain, cognitive problems)

• The respiratory system is typically affected first since mold spores are primarily inhaled

• People with asthma, allergies, or weakened immune systems face higher risks from exposure

• Long-term exposure can lead to chronic health issues including persistent respiratory problems and cognitive symptoms

• Symptom patterns—worse in certain locations, improving when away—can help identify mould as a cause

• Medical evaluation is important for persistent symptoms, especially breathing problems

• Effective management requires both medical treatment and addressing the environmental mould source

• Prevention through humidity control, proper ventilation, and prompt leak repair is the best long-term strategy

If you suspect mould is affecting your health, start by documenting your symptoms and their patterns. Inspect your home for visible mold and signs of moisture problems. Most importantly, don’t ignore persistent symptoms—consult a healthcare professional and consider professional mold testing to get clear answers about what you’re dealing with.