MCS is a final common pathway that several different upstream problems can feed into — and several of those problems are testable with standard lab work. This page lists the tests in priority order, tells you where each one is available, and gives you the exact words to use with your doctor.
There is no single “MCS test” — but there is a short, priority-ordered panel that can identify which treatable mechanisms are active in your case: one genetic blood test (HLA-DR), a set of inflammation markers (the CIRS panel), two mast cell markers, testing of your home, and one free screening questionnaire (the QEESI). Almost all of it is standard lab work any physician can order, even one who has never heard of MCS.
Testing is worth doing before concluding you are out of options. A negative result does not mean your sensitivity is not real — it narrows the search. A positive result can mean there is a specific, treatable condition underneath the sensitivity.
A targeted panel of blood tests, genetic testing, environmental testing, and screening tools can identify which upstream mechanisms are active in your case. Most of these are standard lab tests available through any physician.
A one-time blood test through LabCorp or Quest that identifies whether you carry gene variants associated with impaired biotoxin clearance. For patients where biotoxin or mold exposure is suspected, a positive result supports exploring a CIRS-oriented workup. It is a selective tool rather than a universal first step — many people with MCS do not have HLA susceptibility, and a negative result does not rule out chemical sensitivity. Results are permanent. An online calculator at myhousemakesmesick.com converts your results into susceptibility categories. Ask your doctor to order “HLA-DR/DQ typing by PCR.” The full science of what this test looks for is on the biotoxin science page.
If HLA testing shows susceptibility, the following blood markers map the extent of CIRS involvement: TGF-β1, C4a, MMP-9, MSH (melanocyte-stimulating hormone), VIP (vasoactive intestinal peptide), VEGF, ADH/osmolality, and antigliadin antibodies. Your physician can order all of these through standard labs. Visual Contrast Sensitivity (VCS) testing — available as a free online screening at survivingmold.com — provides an initial neurological indicator.
Serum tryptase and plasma histamine levels can indicate mast cell overactivation. Tryptase is the more reliable marker for baseline mast cell status. If tryptase is elevated or if symptoms strongly suggest MCAS (flushing, hives, GI disturbance, anaphylactoid episodes), a trial of mast cell stabilizers may be warranted even with borderline labs. Some MCAS patients have normal tryptase between flares — so a normal result does not rule it out.
ERMI (Environmental Relative Moldiness Index) or HERTSMI-2 testing for your current home determines whether ongoing mold exposure is feeding the problem. No treatment works while exposure continues. The Hayward Score provides a free initial home health assessment.
The QEESI (Quick Environmental Exposure and Sensitivity Inventory) is the gold-standard screening tool for chemical intolerance. It quantifies your sensitivity levels across chemical, food, and drug categories and provides a baseline against which you can measure improvement over time. Available as a free download through tiltresearch.org. Take it now, save your scores, retake every 3 months during treatment.
If you have persistent GI symptoms, unexplained eosinophilia, or a history of foreign travel, well water, or an acute GI illness that never fully resolved, a single negative stool test is not enough to rule out a parasitic infection.
For some organisms, no amount of time passing rules it out either.
The standard stool ova-and-parasite panel is a microscopy test, and its sensitivity for the organisms most relevant here is materially lower than most patients — and many physicians — assume. Multiplex PCR stool panels do better, but performance varies by platform: one comparison found Giardia sensitivity ranging from 41% to 89% depending on which commercial assay was used. Tissue-dwelling parasites are not detected by any stool test at all; that requires a separate serology order that is rarely placed. And eosinophil count is commonly normal even in chronic infection, so a normal count on its own doesn’t rule anything out either.
Duration of illness doesn’t rule it out. Some organisms persist for decades — Strongyloides can maintain an active infection for the life of the host; one documented case was diagnosed more than 75 years after the only known exposure, with negative stool tests throughout and persistent hypereosinophilia as the only clue.
What this page will not claim: that parasitic infection causes MCS, or that it’s a common driver of chemical sensitivity. No study has examined that link specifically, and this site does not present hypotheses as findings. What the evidence does support is narrower and still useful — a negative test result from a decade ago, or a normal eosinophil count, does not mean the question has actually been answered. If your case includes the pattern above, it may be worth asking your doctor whether a more thorough workup was ever done.
Start with the ISEAI directory of practitioners trained in environmental illness, because most primary care doctors are not. You can also bring this page to your current doctor — these are ordinary labs, not specialist ones.
Most primary care physicians are not trained in CIRS, MCAS, or environmental medicine. The International Society for Environmentally Acquired Illness (ISEAI) maintains a directory of practitioners experienced in these conditions. You can also bring this page to your current doctor — the tests listed above are all standard lab panels that any physician can order, even if they are unfamiliar with the interpretation framework.
If your doctor is unfamiliar with CIRS or HLA testing, here is how to frame the request:
“I have chemical sensitivity and I’d like to investigate whether I have a genetic susceptibility to biotoxin illness. I’d like to order HLA-DR/DQ typing by PCR through LabCorp or Quest. I’d also like a panel including TGF-beta-1, C4a, MMP-9, MSH, VIP, VEGF, and ADH with osmolality. These are standard blood tests. I can provide published references if helpful.”
Every test listed above has a standard lab code. None of them are experimental. Your doctor does not need to understand the interpretation framework to order them — they just need to write the order. You can interpret the results with an ISEAI practitioner afterward, even by telehealth.
If your doctor refuses: You are entitled to request tests. If your primary care physician will not order them, an environmental medicine practitioner, functional medicine doctor, or ISEAI-listed physician will. Many ISEAI practitioners offer initial telehealth consultations specifically for test ordering and interpretation, which is essential for MCS patients who cannot physically enter a medical office.
Once you have results: the Getting Better page walks through which treatment pathway each result points to, and how to put the pieces together into a recovery plan. For the deeper science behind the HLA and biotoxin tests, see Mold Biotoxin Science. For a full explanation of additional tests worth discussing (mycotoxin urine, stool analysis, heavy metals, tick-borne panels), see Medical Care Navigation.
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