Yes, mold can cause lung infections, but it does not happen to everyone. Most healthy people breathe in mold spores daily without any problem. The real risk is for people with weakened immune systems, chronic lung conditions, or severe allergies.
This guide explains how it happens, who is at risk, and what you can do about it.
Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. If you are experiencing respiratory symptoms you believe may be related to mold exposure, consult a qualified healthcare provider immediately.
How Mold Affects Your Lungs
Mold reproduces by releasing microscopic spores into the air. When you breathe those spores in, your body’s immune system usually clears them without any issue. But when the immune system cannot keep up, or when spore concentrations are high enough, those spores can settle in the lungs and cause problems.
Allergic Reactions
This is the most common lung response to mold. Your immune system treats the spores as a threat and overreacts with inflammation. Symptoms include coughing, wheezing, nasal congestion, and shortness of breath. These reactions can range from mild seasonal-allergy symptoms to severe asthma attacks.
Irritation Without Infection
Even in people who are not allergic, high concentrations of mold spores can irritate the airways directly. Prolonged exposure in a poorly ventilated space, like a small NYC apartment with hidden mold, can cause persistent coughing, throat irritation, and breathing discomfort without an actual infection taking hold.
Actual Lung Infection
In the most serious cases, mold does not just irritate or trigger allergies. It colonizes lung tissue and grows inside the body. This is a true fungal lung infection, and it requires medical treatment. These infections are uncommon in healthy individuals but can be severe or life-threatening in vulnerable populations.
Types of Mold-Related Lung Infections
Not all mold-related lung conditions are the same. The CDC and Mayo Clinic identify several distinct types of aspergillosis, the most common mold-related lung infection.
Allergic Bronchopulmonary Aspergillosis (ABPA)
This occurs when the immune system has a severe allergic response to Aspergillus spores in the lungs. It is most common in people with asthma or cystic fibrosis. ABPA causes wheezing, shortness of breath, coughing up brown mucus, and worsening asthma symptoms. It does not mean the mold is actively growing in the lungs, but the allergic inflammation can cause lasting damage if untreated.
Aspergilloma (Fungus Ball)
When someone has existing lung damage from conditions like tuberculosis, emphysema, or sarcoidosis, Aspergillus can grow inside the air cavities that these diseases create. The fungus forms a tangled mass called an aspergilloma or fungus ball. It may cause no symptoms initially but can eventually lead to persistent cough and coughing up blood.
Chronic Pulmonary Aspergillosis
This is a slowly progressing lung infection that typically affects people with underlying lung conditions. Symptoms develop gradually over weeks or months and include weight loss, fatigue, chronic cough, and shortness of breath. It can be mistaken for other conditions, which often delays diagnosis.
Invasive Aspergillosis
This is the most severe and life-threatening form. It occurs when the fungus spreads from the lungs into the bloodstream and reaches other organs like the brain, heart, or kidneys. Invasive aspergillosis almost exclusively affects people with severely compromised immune systems, including organ transplant recipients, chemotherapy patients, and those with advanced HIV/AIDS.
Which Molds Cause Lung Infections?
Not every type of household mold is equally dangerous when it comes to lung infections. However, several species commonly found in homes can pose risks.
Aspergillus
This is the primary mold species responsible for fungal lung infections. Aspergillus fumigatus is the most common cause of aspergillosis in humans. It is found both indoors and outdoors and grows readily on damp building materials, dust, and decaying organic matter.
Stachybotrys (Black Mold)
Often called “black mold,” Stachybotrys chartarum produces mycotoxins that can cause respiratory irritation and immune responses. Despite its reputation, the CDC notes that black mold is not more inherently dangerous than other mold types based on color alone. Our guide on mold vs. black mold explains the differences in detail.
Cladosporium, Penicillium, and Alternaria
These are among the most common mold types found in NYC homes. While they are less likely to cause true lung infections in healthy people, they are potent allergens and irritants that can trigger or worsen asthma, chronic coughing, and respiratory inflammation with prolonged exposure.
Who Is Most at Risk?
Mold-related lung infections are not an equal-opportunity threat. Certain groups face significantly higher risk.
People With Compromised Immune Systems
Organ transplant recipients, cancer patients on chemotherapy, people taking long-term corticosteroids, and individuals with HIV/AIDS have immune systems that cannot fight off fungal spores effectively. For these individuals, even routine indoor mold exposure can lead to serious infection.
People With Chronic Lung Disease
Asthma, COPD, cystic fibrosis, tuberculosis, and sarcoidosis all create conditions in the lungs that make them more vulnerable to mold colonization. Damaged airways, existing inflammation, and structural changes in lung tissue give mold spores places to settle and grow.
Elderly Individuals
Aging naturally weakens the immune response. Elderly residents in older NYC buildings with persistent moisture problems face a compounded risk from both age-related immune decline and higher mold exposure.
Children
Children’s lungs are still developing, and their airways are smaller. They breathe faster than adults, taking in more air relative to their body weight, which means more spore exposure. The CDC has linked childhood mold exposure to the development of new asthma cases.
Symptoms That Should Not Be Ignored
Many mold-related respiratory symptoms overlap with common allergies and colds. The key difference is that mold symptoms persist as long as the exposure continues.
Early Warning Signs
- Persistent cough that does not respond to typical cold medication
- Wheezing or shortness of breath that worsens indoors
- Nasal congestion and sinus pressure that lasts weeks
- Throat irritation and hoarseness
- Fatigue that does not improve with rest
Signs of a More Serious Infection
- Coughing up blood or brown/dark-colored mucus
- Fever combined with breathing difficulty
- Unexplained weight loss
- Chest pain when breathing deeply
- Symptoms that worsen rapidly over days
If you experience any of the serious symptoms listed above, seek medical attention immediately. These can indicate an active fungal lung infection that requires prompt diagnosis and treatment.
How Mold Lung Infections Are Diagnosed
Diagnosing a mold-related lung infection involves several steps because the symptoms overlap with many other respiratory conditions.
Medical History and Risk Assessment
Your doctor will ask about your living conditions, known mold exposure, immune status, and pre-existing lung conditions. Mentioning that you live in an older building or have had recent water damage can be an important diagnostic clue.
Imaging Tests
Chest X-rays and CT scans can reveal fungal masses, lung cavities, and areas of inflammation caused by Aspergillus colonization. These imaging findings often prompt further testing.
Blood and Skin Tests
Blood tests can detect antibodies and immune markers specific to Aspergillus. Elevated IgE levels and eosinophil counts help confirm allergic forms of aspergillosis. Skin prick tests can identify sensitivity to Aspergillus antigens.
Sputum Culture and Biopsy
Mucus samples can be cultured in a lab to identify the presence of mold species. In some cases, a lung tissue biopsy is needed to confirm invasive aspergillosis, particularly when other tests are inconclusive.
The Connection Between Indoor Mold and Lung Health
Living or working in a mold-contaminated space does not guarantee you will develop a lung infection. But prolonged exposure increases the risk for everyone, not just high-risk groups.
NYC-Specific Risks
New York City’s older building stock, shared ventilation systems, and dense living conditions create environments where mold spore concentrations can build up quickly.
Interior bathrooms with no windows, kitchens with poor exhaust ventilation, and apartments with chronic plumbing issues all contribute to sustained indoor mold exposure that goes well beyond occasional contact.
Why Indoor Air Quality Matters
The air inside your home can contain significantly higher mold spore concentrations than outdoor air, especially if hidden mold is growing behind walls or inside ductwork. Professional indoor air quality testing can measure spore levels and identify whether your home’s air is contributing to respiratory symptoms.
The Role of Hidden Mold
You do not need to see mold for it to affect your lungs. Mold growing behind walls, under floors, inside HVAC systems, and in ceiling cavities releases spores into the air you breathe every day. This kind of hidden, ongoing exposure is what leads to chronic symptoms that people often mistake for persistent allergies or recurring colds.
How to Reduce Your Risk
You cannot eliminate mold spores from your environment entirely. They exist everywhere. But you can control the conditions that allow mold to grow indoors and reduce your exposure.
Control Indoor Humidity
Keep humidity below 50%. Use dehumidifiers in rooms that stay damp, run exhaust fans during and after cooking and bathing, and fix any source of standing water or condensation immediately.
Fix Moisture Problems Fast
Mold begins growing within 24 to 48 hours of water exposure. Repairing leaks, drying water damage quickly, and addressing condensation issues are the most effective prevention measures. Our guide on preventing mold growth covers practical steps you can take right now.
Get a Professional Inspection
If you suspect mold in your home, whether from a persistent musty smell, visible growth, recent water damage, or unexplained respiratory symptoms, a professional inspection is the fastest way to get answers. A licensed assessor will locate hidden mold, identify the moisture source, and collect air samples to determine what you are actually breathing.
Not sure what the process looks like? Our mold inspection checklist walks you through what to expect. And if you want to understand the difference between visual inspection and lab testing, our guide on mold testing vs. mold inspection explains when you need each.
Final Thoughts
Mold can cause lung infections, but understanding your risk level and acting on early symptoms makes a significant difference. If you suspect mold in your NYC home and are experiencing respiratory issues, do not wait. Schedule a GAC Environmental mold inspection and protect the air you breathe.