The National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health (NIH), recognizes that mold releases spores that can irritate the nose and lungs. According to the NIEHS, mold exposure can increase the risk of developing asthma or worsen its symptoms. The institute also links extended exposure to memory loss, dizziness, and the loss of cognitive function often called "brain fog."
The NIEHS further reports that long-term exposure to inhaled mycotoxins, the toxic compounds some molds produce, may promote inflammation and affect the immune system. Because mold can affect people in such different ways, physicians rely on several kinds of medical testing. This article explains the four tests that people involved in mold cases encounter most often, so that you know what each one measures and why it matters.
Mold cases generally involve two kinds of evidence. The first is environmental testing of the home or building, in which an industrial hygienist or mold inspector collects air and swab samples for laboratory analysis. That testing shows which molds are present and in what amounts. The second kind of evidence is medical testing of the person, which shows how the body has responded to the exposure.
The two kinds of testing work best together. When the molds found in the home match the molds that a person's tests react to, the results tell a consistent story. A physician can then explain the connection between the building and the illness. The four medical tests described below are the ones that most often appear in that discussion.
Allergy testing looks for immunoglobulin E (IgE), the antibody the body produces in an allergic reaction. An allergist can test for it in two ways. In a skin test, the allergist places small amounts of mold extracts on or just under the skin and watches for a raised, red reaction. The IgE blood test measures the same antibody in a sample of blood.
Both tests can identify reactions to specific molds, such as Alternaria, Cladosporium, Aspergillus, and Penicillium. Allergists use these tests routinely, and the results appear in ordinary medical records. A positive result to a mold that also turned up in the home's air or swab samples gives the physician a direct, specific link between the person and the building.
Immunoglobulin G (IgG) is a different antibody. It forms as the immune system responds to repeated or prolonged contact with a substance, including mold. The IgG test uses an ordinary blood draw, and laboratories can report results for individual mold species.
The IgG test serves a different purpose than allergy testing. Rather than showing an allergic reaction, it shows that the body has encountered a particular mold and has mounted an immune response to it. For that reason, physicians often use IgG results as evidence of exposure, particularly when the species detected match those found in the home.
Some molds produce mycotoxins, the compounds the NIEHS associates with inflammation and immune effects. The urine mycotoxin test looks for these compounds in a urine sample. Commonly reported mycotoxins include ochratoxin A, aflatoxins, trichothecenes, and gliotoxin, which certain species of Aspergillus, Penicillium, and Stachybotrys can produce.
This test differs from the antibody tests because it looks for the toxins themselves rather than the body's reaction to the mold. Some physicians collect the sample after a short sauna session or other measures intended to help the body release stored toxins. When the mycotoxins found correspond to the molds identified in the home, the result adds another point of connection.
Human leukocyte antigen (HLA) testing is a genetic blood test, usually for the HLA-DR and HLA-DQ types. These genes help govern how the immune system recognizes and clears foreign substances. Certain HLA types are associated with greater difficulty clearing mold toxins, which can leave some people more susceptible to illness after exposure.
Because the test looks at genes, the result does not change over time, and the timing of the blood draw does not matter. The HLA test often answers a common question in mold cases: why one person in a household becomes ill while another does not. Two people can share the same exposure and react very differently because of their genetic makeup.
No single test tells the whole story. Allergy testing shows a reaction, IgG shows exposure, urine testing looks for the toxins, and HLA testing helps explain individual susceptibility. Taken together with environmental testing of the home, these results allow a physician to evaluate whether the building caused or contributed to the illness.
Your own physician decides which tests are appropriate for you. If you develop new symptoms after exposure to mold or water-damaged building materials, including exposure you did not realize at the time, you should see a doctor. Keeping copies of your test results, your medical records, and any inspection reports helps preserve the evidence.
Christopher L. Beard, an Annapolis attorney, concentrates his practice in toxic mold injury and habitability claims for Maryland tenants. If you have questions about mold in your home or workplace, e-mail chris@attorneybeard.com or call (410) 267-0227. You can also return to the attorneybeard.com home page.
Source: National Institute of Environmental Health Sciences, "Mold", and "Mold and Your Health" (March 2025).
