From Brain Fog to Fatigue: How Mould Toxicity Affects the Nervous System & Hormones

We’ve all had days where we feel flat, foggy, or completely drained for no obvious reason. But what if those symptoms — the constant fatigue, forgetfulness, poor concentration, or mood swings — weren’t about stress or getting older at all? What if the real cause was something in your environment?

For many people, prolonged exposure to mould and the toxins it releases can quietly disrupt the body’s delicate balance — not just in the lungs or sinuses, but in the nervous and hormonal systems too. These toxins, known as mycotoxins, can interfere with how the brain communicates with the body, disrupt hormone production, and even impair cellular energy.

Over time, this internal chaos can lead to what feels like burnout — but is actually a biological response to environmental stress. People often describe it as feeling “wired but tired,” emotionally unstable, or hypersensitive to light, sound, and smells.

In this article, we’ll explore how mould toxicity affects the brain, nervous system, and hormones — and why recognising the connection between mould exposure and neurological symptoms is key to restoring your energy, focus, and emotional balance.

How does mould affect the brain?

The brain is one of the most sensitive organs in the body — and also one of the most easily affected by toxins. When exposed to mould, it’s not just your sinuses or lungs that suffer. The mycotoxins released by certain species of mould (such as Aspergillus, Stachybotrys, and Penicillium) can travel through the bloodstream, cross the blood–brain barrier, and trigger inflammation inside the brain itself.

This inflammation is called neuroinflammation, and it’s one of the primary ways mould toxicity affects the nervous system. Once mycotoxins reach the brain, they irritate nerve tissue and disrupt the normal balance of neurotransmitters — the chemical messengers responsible for mood, memory, and focus.

As a result, people exposed to toxic mould often experience a range of neurological symptoms such as:

• “Brain fog” or mental sluggishness
  
• Poor short-term memory and word-finding difficulties
  
• Difficulty concentrating or processing information
  
• Heightened anxiety or emotional reactivity
  
• Headaches, dizziness, or sensitivity to light and sound

The biological chain reaction

When the immune system detects mould toxins, it releases inflammatory molecules called cytokines to fight them off. In small doses, this response is protective — but with ongoing exposure, these cytokines begin to circulate persistently, reaching the brain and causing inflammation there too.

This is where symptoms like brain fog, confusion, and poor concentration begin. The inflammation interferes with the brain’s ability to transmit signals efficiently, much like static on a radio line. Over time, this can even affect the limbic system — the brain’s emotional centre — making people more prone to anxiety, irritability, and sensory overload.

In some cases, mould exposure can also reduce blood flow and oxygen delivery to the brain, particularly if key molecules like VEGF (Vascular Endothelial Growth Factor) are suppressed — a finding often seen in people with CIRS (Chronic Inflammatory Response Syndrome). Lower oxygen means less cellular energy, which explains why people often feel both mentally foggy and physically exhausted at the same time.

How mould affects brain energy

Another crucial piece of the puzzle is the mitochondria — the tiny “power plants” inside every cell. Mycotoxins can damage or inhibit mitochondrial function, preventing them from producing adequate ATP (adenosine triphosphate), the molecule that fuels nearly every brain and body process.

When this happens, it’s not just your muscles that feel weak — your brain runs low on energy too. Tasks that used to feel effortless, like remembering details, making decisions, or staying alert, suddenly become draining. This mitochondrial disruption also contributes to the “crash” many people experience after mild activity — a hallmark symptom of mould-related illness and chronic fatigue.

When the nervous system gets stuck in survival mode

One of the lesser-known effects of mould toxicity is how it disrupts the communication between the brain and body, keeping the nervous system in a constant state of alert. 

When mould toxins inflame or overstimulate these systems, the body can become hypersensitive to its surroundings.This overactivation is part of what Dr Neil Nathan, an environmental medicine specialist and author known for his work on mould illness, chronic fatigue, and complex environmental sensitivities, describes as “limbic system hypersensitivity.” 

In a podcast discussion with Dave Asprey (The Human Upgrade, Episode 733), Dr Nathan explains that after prolonged mould exposure, the brain’s limbic system can become retrained to stay in constant defence mode — perceiving threat long after the original exposure has ended. In this state, even small stressors can trigger a “fight or flight” response, leading to:

• Increased heart rate or shallow breathing
  
• Difficulty relaxing or falling asleep
  
• Digestive changes (due to vagus nerve dysregulation)
  
• Heightened emotional reactivity

Healing from mould toxicity 

Recovering from mould toxicity isn’t just about removing exposure — it’s also about helping the body and brain recover from the stress they’ve been under. Once the immune and nervous systems have been overactivated for a long time, they need time, support, and the right environment to find balance again.

As Dr Neil Nathan emphasises, the process of healing from mould toxicity begins with calming the nervous system. Only once the body feels safe can detoxification, hormonal repair, and energy restoration truly begin.

Here’s how to support your recovery step by step:

1. Calm the nervous system first

Your brain can’t heal if it still believes you’re in danger. Start by creating a sense of physical and emotional safety.

• Reduce sensory stress: Limit bright lights, strong smells, and noise if you’ve developed sensitivities.
  
• Practice deep breathing and grounding techniques: Slow breathing activates the vagus nerve, helping switch the body from “fight or flight” to “rest and repair.”
  
• Gentle movement: Try yoga, walking, or stretching to improve circulation and signal to the body that it’s safe to relax.
  
• Prioritise rest: Overexertion can trigger inflammation and setbacks — recovery happens when the nervous system is calm, not when it’s pushed.

2. Support cellular and mitochondrial health

Because mould toxins can damage mitochondria, restoring energy production is key.

• Stay hydrated and include electrolyte-rich fluids to support detoxification.
  
• Eat foods high in antioxidants (berries, leafy greens, turmeric, olive oil) to reduce inflammation.
  
• Support mitochondrial repair with nutrients like magnesium, CoQ10, B vitamins, and omega-3 fatty acids.
  
• Avoid excess caffeine and sugar, which can further stress the adrenals and cause energy crashes.

3. Balance hormones naturally

Chronic inflammation can suppress the pituitary, thyroid, and adrenal glands, disrupting hormones like cortisol, thyroid hormones (T3, T4), and sex hormones.

• Keep blood sugar stable by eating regular, balanced meals with protein and healthy fats.
  
• Get morning sunlight exposure to help reset circadian rhythm and support cortisol balance.
  
• Focus on consistent sleep — aim for 7–9 hours in a dark, cool room.
  
• Consider herbal adaptogens such as ashwagandha or rhodiola (under professional guidance), which can help restore adrenal balance and stress resilience.

4. Prioritise clean air and environment

Even after leaving the source of mould exposure, maintaining clean indoor air helps prevent relapse.

• Use HEPA air purifiers and control humidity (ideally 40–50%).
  
• Keep airways clear with natural lung-support tools like the AirPhysio devices, which helps improve breathing capacity.
  
• To control residual airborne mould spores, products such as SAN-AIR’s mould prevention and air purifying gels can help keep your environment fresh and low in microbial load.

Read related article: Preventing Mould Before It Starts: A Step-by-Step Guide

5. Seek professional guidance

If your symptoms persist or are severe, work with a healthcare practitioner trained in environmental or functional medicine. They can assess inflammation markers, guide detox support, and ensure treatment is tailored to your individual biochemistry.

Conclusion: Healing the mind and body, one step at a time

Your body isn’t broken — it’s simply reacting to an overload of environmental stress, especially when you’re experiencing mould toxicity or Chronic Inflammatory Response Syndrome (CIRS). 

Once the source of exposure is removed and the nervous system is given the right support, healing can begin. By focusing on calming inflammation, supporting mitochondrial energy, and restoring hormonal balance, you can help your body return to its natural rhythm.

Creating a clean, low-toxin environment is an essential part of this process. Using air-purifying and mould-prevention products can help reduce ongoing exposure and support long-term recovery. Combine that with balanced nutrition, proper rest, and mindful stress management, these small steps create the foundation for genuine, lasting improvement.

Your Recovery Starts Here: Products That Care for You and Your Environment