Mould Allergy Symptoms

What Causes Mould Allergy?

Key takeaway:

Mould allergies develop when your immune system overreacts to mould spores—tiny “seeds” released by mould that float through the air.

When inhaled, mould spores trigger histamine release, leading to allergy symptoms similar to pollen or dust allergies. Mould is everywhere, but damp indoor environments—such as bathrooms, basements, or poorly ventilated homes—can lead to higher concentrations and more severe reactions.

Common Mould Allergy Symptoms

Key takeaway:

Mould allergy affects the respiratory system, skin, and sometimes the sinuses or lungs.

Typical symptoms include:

• Sneezing or nasal congestion
• Runny or blocked nose
• Itchy, red, or watery eyes
• Post-nasal drip or throat irritation
• Coughing or wheezing (especially at night)
• Itchy skin, rashes, or hives
• Aggravation of asthma or sinus infections
• Fatigue and brain fog (in chronic exposure)

In more sensitive individuals, symptoms can also include chest tightness, sinus pressure, or difficulty breathing—especially when exposed to mouldy buildings or after rain.

Mould Allergy vs Mould Toxicity

Key takeaway:

Mould allergy and mould toxicity are not the same—and understanding the difference is crucial.

Most of the information you’ll find online relates to mould allergy. This is different to mould toxicity. Mould allergy is an immune response to mould spores in your environment, which mould toxicity is an accumulation of mycotoxins inside your body.

If you have mould allergy, you’ve obviously been exposed to mould in your environment, which means you may also have mould toxicity.

Mould toxicity is a greater concern as it may linger and cause much more widespread and serious symptoms than mould allergy. The two can appear together or separately.

When and Where Symptoms Appear

Key takeaway:

Mould allergy symptoms can flare up seasonally or year-round, depending on exposure.

• Outdoor mould allergies often worsen in late summer and autumn due to decaying leaves, compost, and “leaf mould.”
• Indoor mould allergies can persist all year, especially in damp homes or workplaces.
• Hidden mould—behind walls, under flooring, or in HVAC systems—can trigger constant symptoms without visible signs.

If your symptoms improve when you’re away from home or worsen in damp weather, mould is a likely culprit. If you have recurrent symptoms of mould allergy, you should probably get tested for mould toxicity, as repeated or ongoing mould exposure is likely to cause mould toxicity. If you are concerned that you may have mould toxicity, assess your risk using this Mould Illness Questionnaire.

Mould Allergy Rash and Skin Symptoms

Key takeaway:

Skin reactions are common in mould allergy and can look like eczema, hives, and itching.

When mould spores contact the skin or are inhaled, the immune system can trigger histamine-mediated inflammation, leading to:

• Red, itchy rashes
• Eczema flare-ups
• Hives or welts
• Burning or peeling skin
• Increased sensitivity to fabrics or tags

These symptoms can overlap with mould toxicity–related skin issues, so if you’re experiencing these symptoms, you should definitely rule out ongoing mould exposure. Take a look at our blog post Mould: Rashes, Eczema & Itching for more information.

Who Is Most at Risk?

Key takeaway:

Certain groups are more prone to mould allergy and its complications.

You’re at higher risk if you:

• Have asthma, hay fever, or other allergies
• Live or work in damp or poorly ventilated buildings
• Are exposed to mould through farming, gardening, or composting
• Have a weakened immune system
• Are a child, elderly person, or pregnant woman (increased vulnerability to inflammation)

How to Manage Mould Allergy Symptoms

Key takeaway:

Reducing exposure is the most effective way to prevent mould allergy symptoms.

If you have mould in your environment, no matter how little, you must take it seriously. Mould grows when there is a damp issue and very often, what you see is just the tip of the iceberg. Even mould growing unseen behind walls can affect your health.

If you have mould at home, report it to your rental agency, or get an inspection as soon as possible. Due to the seriousness of the health risk, it’s best to get out of the house until the mould is remediated. All mouldy materials must be removed and the source of the problem needs to be fixed to avoid recurrence.

Taking the Next Step

Key takeaway:

Experiencing symptoms of mould illness can be concerning, but support is available.

It’s completely understandable to feel worried if you’re experiencing any of the symptoms above. Mould illness is complex, but there are practical steps you can take to identify exposure, support your body, and begin recovery.

If you want to learn more, you can download our free ebook Is Mould Making You Unwell?, or contact us directly and we’ll help you get the help you need.