Asthma and Mold: How Damp Buildings Trigger Attacks, and What to Do About It

Of all the health claims made about indoor mold, the link between asthma and mold is the best supported. It is not contested, it is not fringe, and it is the reason a damp home is worth taking seriously even when nobody is alarmed by the look of it.

Related from GPMI: Physician support, independent and lab-based.

The short version

Mold spores are airborne particles. In a person with allergic asthma, inhaling them provokes an immune response that narrows the airways. The result is coughing, wheezing, chest tightness and shortness of breath. The World Health Organization concluded in its guidance on dampness and mold that occupants of damp buildings are at increased risk of respiratory symptoms and asthma.

How mold affects the airways

The allergic reaction

In sensitized people the immune system treats mold spores as a threat. Antibodies trigger allergic responses, inflammatory mediators are released, and the airway lining swells and produces mucus. Reduced lung function follows.

Allergic asthma specifically

Most mold-related asthma is allergic asthma, meaning symptoms are caused by an identified allergen rather than by exercise or cold air. A mold allergy and asthma frequently travel together, alongside allergic rhinitis and hay fever.

Mold allergy symptoms without asthma

Plenty of people get the upper airway version alone: stuffy nose, watery eyes, sneezing and a scratchy throat. Those allergy symptoms occur year round indoors, unlike pollen, which helps tell them apart.

The 3 conditions worth naming

Allergic bronchopulmonary aspergillosis

A specific reaction to Aspergillus fumigatus, one of the most common molds indoors and outdoors. It affects people with asthma and with cystic fibrosis, and it can cause severe asthma that does not respond normally to treatment. It is uncommon, diagnosable, and worth knowing exists.

Hypersensitivity pneumonitis

Inflammation deep in the lungs from repeated exposure to organic dust including mold. Different from asthma and often mistaken for it.

Asthma developing in children

There is reasonable evidence associating damp indoor spaces with the development of asthma in children, not only the worsening of existing asthma. This is about dampness in general rather than any one species.

Risk factors

• A personal or family history of allergies or asthma

• Existing certain allergic conditions such as eczema or hay fever

• Cystic fibrosis

• Living or working in water damaged buildings

• Prolonged time in damp places with poor ventilation

The pattern that identifies a building problem

Symptoms that ease within a day or two of leaving and return within hours of coming back. More than 1 person in the household affected. Onset following water damage. Bring that pattern and your medical history to a physician. It is far more useful than a symptom list, and it is what separates a building cause from other symptoms with other explanations.

Where mold grows in a home

Excess moisture, always

The most common molds indoors, Cladosporium, Aspergillus, Penicillium and Alternaria, all need water. Mold growth follows moisture and nothing else.

The usual sources

Roof leaks, plumbing leaks, blocked rain gutters that spill against the wall, poor groundwater drainage around the foundation, and condensation in damp areas.

Air conditioning

An air conditioner is a common and overlooked source. Condensation coils stay wet by design, and a central air conditioning system with a blocked drain line or a standing collection bucket grows mold and then distributes it through every room. Anyone with asthma in a house with central air should have that system checked.

Poor ventilation

A bathroom without a working extractor, a kitchen vented into the attic, a laundry with no outlet. Damp environments are made this way more often than by dramatic leaks.

Reducing exposure

Control indoor humidity

Keep humidity levels between 30 and 50 percent. Above 60 the odds shift decisively toward growth.

Ventilate properly

Run exhaust fans during and after showering and cooking. Make sure rooms are properly ventilated rather than sealed. On dry days, open doors and windows to bring outdoor air through, but not on high pollen or high outdoor mold count days if you are also sensitized to those.

Fix water fast

Address any leak within 24 to 48 hours, which is how quickly growth can begin. Clear rain gutters, and grade soil to promote groundwater drainage away from the foundation.

Filtration

A HEPA filter will trap mold spores in the air passing through it, which helps as a supplement. It does not address wet material, and it is not a substitute for finding the source.

Avoid contact during cleanup

If any cleaning is done, the person with asthma should not be the one doing it and should not be in the room. That single change prevents a lot of avoidable attacks.

Testing, and when it earns its place

Visible growth does not need a laboratory to justify acting. Testing earns its place when:

• Someone has asthma symptoms that track the building but nothing is visible

• Air sampling can compare indoor mold counts against an outdoor baseline

• A physician wants to know what a patient is actually exposed to

• A landlord, insurer or buyer needs documentation

We work directly with referring physicians, because what a doctor needs is a measurement, not an opinion about how a wall looked.

What we do and do not do

We provide independent mold inspection and air quality testing. We inspect and test only. We never perform remediation and take no fee from any cleanup, so our findings carry no commercial direction.

We do not diagnose asthma and we do not treat it. Nothing here replaces a physician. What we can tell you is what is in your air and where the water is coming from, which is the half of the problem your doctor cannot see.

Common questions

Can mold cause asthma, or only trigger it?

Both are supported. It reliably triggers attacks in people who already have asthma, and damp housing is associated with children developing it.

Do I need to leave my home?

Usually not. It depends on severity and on how quickly the moisture can be addressed. That is a decision for you and your physician, informed by measurements.

Will an air purifier fix it?

It helps with airborne particles. It does nothing about the wet material producing them.

Is mildew a problem for asthma too?

Surface mildew in a bathroom is a much smaller exposure than growth inside a wall cavity, but in a sensitized person it can still trigger symptoms.

How do I know if it is mold rather than dust or pollen?

Timing. Pollen is seasonal. Mold-related symptoms occur year round and track the building rather than the calendar. Allergy testing can confirm which allergens you actually react to.

Get the measurement

We provide independent mold inspection and laboratory air testing across Orange County, Los Angeles and Pasadena. If somebody in the house has asthma and the house has been wet, that is worth measuring rather than guessing about.

Where this fits

• Symptoms of black mold exposure, what the evidence supports and what it does not, marked as what each one is
• How we support referring physicians