How Mould Affects Your Immune System

Your immune system is your body’s defence against disease, infection, and environmental threats. But what happens when the threat is invisible, constant, and living inside your own home? Mould exposure doesn’t just cause sneezing and coughing — it fundamentally alters how your immune system functions, and the effects can persist long after the exposure ends.

Mould and Immune System Activation

When you inhale mould spores, your immune system mounts an inflammatory response. This is normal and protective in the short term. But when exposure is chronic — as it is when you’re living in a mouldy home — the immune system remains in a state of constant activation. This chronic inflammatory state diverts resources from other immune functions, leaving you more susceptible to infections, slower to heal, and generally feeling unwell. It’s like an army that’s been fighting one battle for so long it can’t respond to new threats.

Understanding what causes mould helps explain why persistent dampness creates the conditions for this chronic immune challenge.

The Three Immune Pathways

Mould affects the immune system through three distinct mechanisms:

• Allergic (IgE-mediated): The immune system produces IgE antibodies against mould proteins, triggering histamine release and classic allergy symptoms
• Inflammatory (innate immunity): Mould fragments and mycotoxins activate innate immune cells, producing pro-inflammatory cytokines that cause systemic inflammation
• Immunosuppressive: Certain mycotoxins (particularly from Aspergillus and Stachybotrys) directly suppress immune cell function, reducing your ability to fight infections

Signs Your Immune System Is Affected

Chronic mould exposure may be affecting your immune system if you experience: recurring colds, flu, or sinus infections; slow wound healing; persistent fatigue that doesn’t improve with rest; new food sensitivities or allergies; autoimmune symptoms (joint pain, skin reactions); and chronic low-grade malaise. These symptoms often develop gradually, making the connection to mould exposure difficult to identify.

If you’re experiencing these symptoms, take our mould risk assessment to evaluate whether your home environment could be the underlying cause.

Chronic Inflammatory Response Syndrome (CIRS)

In genetically susceptible individuals (estimated at 25% of the population), mould exposure can trigger Chronic Inflammatory Response Syndrome — a multi-system inflammatory condition. CIRS involves dysregulation of the innate immune system, leading to chronic fatigue, cognitive impairment, joint pain, gastrointestinal disturbance, and hormonal disruption. Diagnosis requires specific biomarker testing, and treatment involves both environmental remediation and medical intervention. For more on long-term impacts, see our article on long-term effects of mould exposure.

Recovery and Remediation

The good news is that immune function typically recovers once mould exposure is eliminated. mould testing can identify hidden mould sources that may be driving chronic immune activation. Following professional remediation by mould removal services in Hobart, most people report gradual improvement in immune-related symptoms over 3-6 months. Supporting recovery with adequate sleep, nutrition, and stress management helps the immune system reset to normal function.