Is There a Blood Test for Mould Illness?

Yes — there are two main blood tests related to mould illness. One identifies allergy to mould spores, and the other detects immune reactions to mycotoxins (toxins produced by mould).

Each test provides different information. However, blood tests alone rarely give the full picture, and many practitioners recommend urinary mycotoxin testing as the first step for assessing mould illness.

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Lia de Lancey BSc MSc DipNT MNBP
Trained with MastCell360 & Dr Jill Crista, specialising in mould illness and mineral nutritional balancing.
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Key takeaway:

There is a blood test for mould—but which one you need depends on whether you’re looking for a mould allergy or mould toxicity.

Mainstream medicine offers a blood test to check for allergic reactions to mould spores, while mould illness experts may use a mycotoxin antibody test to detect immune reactions to mould toxins. These two tests measure very different things.

In practice, mould experts usually recommend a urine test instead – a simple, at home test that you can complete yourself without the need for taking blood.

Why Your GP Blood Test Won’t Detect Mould Illness

If you’ve asked your GP about mould-related illness and been offered a blood test, it was almost certainly an IgE allergy test, designed to detect sensitivity to mould spores, not mycotoxin accumulation in the body.  A normal result on this test does not rule out mould illness.

This is one of the most common sources of confusion for people with mould illness.  Standard allergy testing and mould illness testing are measuring completely different things.  The NHS does not currently offer mycotoxin testing and most GPs are not yet familiar with the distinction between mould allergy and mould toxicity.  This gap in mainstream medicine means that people with mould illness frequently receive normal test results and are told there is nothing wrong when in fact they have simply haven’t taken the right test.

The Two Main Types of Mould-Related Blood Tests

Key takeaway:

Mould spore allergy and mould toxin exposure are distinct — and so are the tests.

Mould Spore Allergy Test
  • What it measures: Immune (IgE) reactivity to mould spores — tiny airborne “seeds” released by mould.
  • Purpose: Confirms whether your respiratory or allergy symptoms (like congestion, coughing, or itchy eyes) are triggered by mould exposure.
  • Availability: Widely available through GPs and allergy clinics.
  • Limitations: It doesn’t tell you if mould toxins (mycotoxins) are affecting your body or overall health.
Mycotoxin Antibody Test
  • What it measures: Immune reactions (IgE, IgG) to mycotoxins — the toxic compounds mould releases as a defense mechanism.
  • Purpose: Helps identify whether your immune system has responded to mould toxins, suggesting exposure.
  • Availability: A newer, more specialised test accessed through a particular lab (MyMycoLab).
  • Limitations: May be complicated and more costly to access due to the need for a private phlebotomist. Not ideal for measuring the amount of toxins in your system.

Mould Spores vs Mould Toxins — What’s the Difference?

Key takeaway:

Mould spores and mould toxins are completely different entities, and your body reacts to them in different ways1.

Mould Spores Mould Toxins (Mycotoxins)
What they are Tiny “seeds” that float in the air and grow into mould Toxic compounds produced by mould to defend itself
Where they’re found Air, dust, damp walls, soil Air, inside mouldy materials, dust, and even food
Body reaction Allergy (sneezing, congestion, asthma) Toxicity (many and varied symptoms including fatigue, brain fog, anxiety, mood issues)
Testing IgE blood test (mainstream) Mycotoxin antibody blood test or urinary mycotoxin test

It’s entirely possible to have:

  • Mould allergy without mould toxicity
  • Mould toxicity without mould allergy
  • Or both at the same time

How Useful Are Blood Tests for Mould Illness?

Key takeaway:

Blood tests can provide clues—but may not give the full story.

A mould allergy blood test can confirm if mould spores are triggering your symptoms2. That’s valuable information for allergy management, but it doesn’t reveal whether mould toxins are affecting your wider health. A normal result on a GP mould allergy test simply means you don’t have a mould allergy, which is an entirely different condition to mould toxicity.

A mycotoxin antibody test can help determine whether your immune system has reacted to toxins. This can be particularly helpful if:

  • You’ve tested negative on a urinary mycotoxin test, but still have symptoms suggestive of mould toxicity
  • You want to understand whether you’ve had recent or past exposure

However, most practitioners consider it a backup tool rather than a first-line option as it is harder to access and doesn’t measure toxic load.

Why Urinary Mycotoxin Testing Is Often the First Step

Key takeaway:

If you’re trying to confirm mould illness, urinary mycotoxin testing usually presents an easier first step.

Urinary tests measure the actual mycotoxins your body is eliminating3, giving clearer insight into:

  • Current toxin load
  • Which types of mycotoxins are present

A blood tests can be considered if the urinary mycotoxin test is clear despite symptoms consistent with mould illness.

What to Do Next

If you are concerned about the effects of mould exposure on your health or you’re wondering whether you may have mould illness, you may want to find out more about testing options. There’s a lot more information on this blog post: Can You Get Tested For Mould Exposure?

You can also take this Mould Illness Questionnaire immediately if you’re looking for more immediate feedback. Developed by Dr Jill Crista, one of the leading experts in mould toxicity, it’s well correlated with symptoms she sees in practice.

References

    1. Hope J. A review of the mechanism of injury and treatment approaches for illness resulting from exposure to water-damaged buildings, mold, and mycotoxins. Scientific World Journal. 2013 Apr 18;2013:767482. doi: 10.1155/2013/767482. PMID: 23710148
    2. Mayo Clinic: Mold Allergy: Symptoms and Causes. Mayo Clinic. mayoclinic.org
    3. MosaicDX. MDX Science Snapshot: MycoToxin Testing in Urine vs Serum [Internet]. Overland Park (KS): MosaicDX; 2025 Dec 9 [cited 2026 Apr 9]. Available from: https://mosaicdx.com/resource/mdx-science-snapshot-mycotoxin-testing-in-urine-vs-serum/