How mold impacts the immune system
Important note: The content in this blog post is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare professional regarding any medical concerns or symptoms.
Mold exposure can affect people very differently, and the body’s response isn’t always straightforward. We’ve simplified some of the information here to make the topic easier to understand and navigate, but to deepen your understanding, we highly recommend reviewing the full study.
How is it that two people can live in the same house, yet one seems completely fine while the other experiences a range of mold-related symptoms?
I experienced this while unknowingly living in a moldy home for eight years. I was symptom-free, while my partner was struggling with multiple symptoms related to (as we later learned) mold exposure.
A widely cited report from the American Academy of Pediatrics outlines that mold doesn’t affect the body in just one way. It can impact health by both immune- and non–immune-related processes through inhalation, touch, or ingestion.
From an immune response, molds produce allergens that may lead to sneezing, a runny nose, and red eyes, among other symptoms. Non-immune effects include irritation of mucous membranes, infection, and reactions from toxic (mycotoxins) byproducts. This helps explain why symptoms vary so widely between individuals.
Let’s go into a bit more detail.
Fungi cell walls are partly formed of glucans – these are endotoxin-like substances that stimulate the immune system. During growth, fungi produce 1) enzymes that can be allergenic, 2) metabolites that can be irritating, and 3) mycotoxins that can be toxic.
Mold as an immune system trigger
One part of mold that may play a role in immune system activation is β-D-glucans, compounds found in fungal cell walls. These act similarly to endotoxins and can stimulate immune activity.
When inhaled or contacted, mold can activate the immune system through:
Allergic (IgE-mediated) pathways
Inflammatory responses
Delayed hypersensitivity reactions
This means mold exposure doesn’t just cause one type of reaction. It can trigger multiple layers of immune response simultaneously.
The most well-established effect of mold exposure is allergic stimulation. The immune system produces IgE antibodies, leading to conditions like:
Allergic rhinitis (sneezing, congestion)
Asthma
Allergic fungal sinusitis
The research shows mold can push the immune system toward a “pro-allergy” state, increasing signaling molecules (like interleukins 4 and 5) that promote IgE production and inflammation.
Essentially, mold exposure is like pouring gasoline onto a fire.
In practical terms, the immune system becomes more reactive than necessary, especially in people who are already sensitive. The paper notes that mold exposure is a strong irritant factor and worsens symptoms of preexisting allergic disease in the same manner as other irritants like tobacco smoke.
Other ways mold impacts the body
Some molds produce mycotoxins (primarily found in spores), which can have direct effects on health. The fungi that produce mycotoxins are called “toxigenic fungi,” and the amount, if any, and type of mycotoxin produced depend on a complex set of factors. Because mycotoxin-producing molds are fat-soluble, they’re easily absorbed via the airways or through the skin.
The report I shared above notes that certain mold byproducts (metabolites) are:
Immunotoxic (damaging to immune cells)
Immunosuppressive (reducing immune function)
Cytotoxic (damaging cells broadly)
For example, some compounds can inhibit protein synthesis, interfere with normal cell function, or alter immune signaling pathways.
This highlights an important point: mold can affect the immune system in different ways depending on the person and the type of exposure. In some cases, it may trigger an immune response, while in others, it may interfere with how the body normally responds and recovers.
Why symptoms can feel so broad and inconsistent
For some people, mold may be insignificant. For others, it can be a meaningful piece of the health puzzle. This was the case for us.
Mold has many pathways to affect us, including: 1) trigger allergies (over-activation); 2) cause inflammation (chronic immune signaling); 3) disrupt regulation (misfiring responses); and 4) suppress certain functions (reduced defense).
Because of this, it creates a situation where the immune system can be both activated and impaired at the same time. This helps explain why people may experience various symptoms like:
Respiratory issues
Skin reactions
Fatigue or malaise
Increased susceptibility to other illnesses
The research emphasizes that a person’s response to mold can depend on genetics; immune sensitivity; level and duration of exposure; and overall environmental context (other irritants, allergens, etc.). For example, only a subset of exposed individuals develop conditions like hypersensitivity pneumonitis, even in the same environment.
Tips to reduce mold exposure
It’s impossible to keep mold spores out of the house entirely. They are microscopic and come inside through day-to-day living via windows and doors or small air gaps.
The paper makes the point that the real task is to prevent the spores from colonizing and growing. In other words, the key to mold control is moisture control.
Prevention:
Check for and fix leaks / possible water penetration points
Vent appliances that produce moisture (clothes dryers and stoves) to the outside and use a bathroom fan
Use dehumidifiers (with a target humidity level of below 50%)
Conduct regular mold testing to check for elevated mold levels, or schedule a mold dog inspection
Manage:
Use HEPA filters
Dust thoroughly and regularly (as mold often travels on dust)
Remediation: If it’s possible, the best way to reduce mold exposure is usually to find and properly remove the mold source while fixing the moisture issue that’s allowing it to grow. We never recommend DIYing this. Disturbing mold can spread spores and other particulates throughout the space. Proper remediation requires containment, safety precautions, and an understanding of how to remove contaminated materials without creating additional exposure, especially for those who are already sensitive.
Get in touch
If you’re in the San Francisco Bay Area and want to learn more about our approach to mold dog inspections, give us a call or text: (510) 822-0277.