The Science of Mold Biotoxins & HLA Genetics

Where CIRS stands, stated in the body and not only in a note

That MCS is real and physiological is supported across this site and is not the question here. CIRS is a separate and more contested claim. Its model, biomarker set and treatment sequence were developed within one research group, chiefly through case series and treatment cohorts published by that group;¹² they have not been reproduced by independent investigators, and a 2019 review in a mainstream allergy journal argues that the mycotoxin-injury model as commonly presented is not supported by the toxicology.³ Readers should hold both facts at once: a coherent model from its originators, and no independent confirmation.

What is independently established is narrower and firmer: damp and moldy buildings are associated with respiratory symptoms, asthma development and exacerbation, and allergic and irritant effects, in reviews by the World Health Organization and in the epidemiological literature.⁴⁵ Those effects do not depend on the CIRS mechanism and are reason enough to fix a wet building. What buildings do and do not show as a cause of MCS is on its own Evidence page: Do water-damaged buildings and indoor VOCs cause MCS?.

The HLA-DR hypothesis, as the CIRS literature proposes it

In the model, the HLA-DR proteins that present antigen fragments to T-cells do not, in people carrying certain haplotypes, grip biotoxin fragments effectively; no antibody response is triggered, and the toxin is never tagged for clearance.¹ The originating group groups HLA-DR/DQ haplotypes into susceptibility categories (multi-susceptible, mold-susceptible, post-Lyme and low-MSH types) and reports that a substantial fraction of the population carries at least one such haplotype. That fraction, and the haplotype table itself, come from the group’s own series and have not been confirmed by independent studies.

Two things are true regardless of the model. Human immune recognition, chemical metabolism and oxidative-stress handling do differ between people — that is ordinary biology. And HLA-DR/DQ genotyping is an ordinary, one-time blood test available from clinical laboratories; what is contested is what the result means for biotoxin illness, not whether the test exists.

The recirculation hypothesis

The model holds that untagged biotoxins pass from the liver into bile, are reabsorbed in the small intestine and return to the bloodstream in an enterohepatic loop, so that a person can leave the building and stay ill;¹ and that the loop keeps the innate immune system activated, with sustained cytokine production. The bile-acid sequestrant treatment the group uses is designed to interrupt that loop, and the group’s own time-series and treatment-cohort papers report improvement on it.¹ A 2024 report of four cases from a separate group estimated, from one HLA-DR carrier’s urine samples eighteen months apart, that ochratoxin A left the body with a half-life of about 311 days, roughly ten times slower than expected — a single measurement, consistent with the model’s slow-clearance claim but not a test of it.⁶

MSH depletion and MARCoNS, as proposed

Melanocyte-stimulating hormone is a hypothalamic regulatory peptide with roles in inflammation, sleep, pain modulation and gut-barrier integrity that are described in general physiology. The CIRS model proposes that chronic innate activation suppresses MSH and that low MSH explains the sleep, pain, gut and hormonal symptoms its patients report; the group reports low MSH as one of its biomarkers.¹² The model further proposes that low MSH allows multiply antibiotic-resistant coagulase-negative staphylococci to colonize the deep nasal passages and that their biofilm suppresses MSH further. The MARCoNS mechanism has not been studied outside the CIRS practitioner literature, and it is stated here as that literature’s proposal, not as a finding.

The group’s later imaging work reports structural brain differences on volumetric MRI in patients meeting its case definition;² like the rest of the model it awaits independent replication. Treatment sequences built on these proposals are described, without regimen detail, on the Mold, CIRS & chemical sensitivity page.

What to take from this page

Treat the CIRS model as a testable line of inquiry for a subset of people whose illness followed a water-damaged building, to be pursued with a clinician who can order and interpret the tests — not as settled science and not as the explanation for MCS. Fix the water regardless: the independently established harms of damp buildings need no biotoxin model to justify a leak repaired and wet material removed.