Is the Most Underestimated Health Threat at Home This Summer Tiny Mold Spots?

Indoor mold is a hidden summer health threat linked to Sick Building Syndrome, severe respiratory issues, and even depression. This article outlines three essential steps to combat it: ventilating to control humidity, locating hidden mold, and safely disinfecting or discarding affected items.

In most areas south of the Qinling-Huaihe Line in China, indoor environments are prone to mold for more than half the year. In the north, June, July, and August are also peak seasons for mold growth. Besides walls, mold can grow on desks, chairs, cabinets, clothing, pillows, sinks, floor drains, air conditioners, washing machines, shoes, and everyday household items.

Mold spots are not just visually dirty and highly detrimental to your living experience; they can also bring unexpected physical effects. Your body might experience various uncomfortable symptoms: persistent coughing, a stuffy nose, breathing difficulties, and itchy skin. The problem might be hiding in those spotted corners—invisible, microscopic mold could be the culprit behind your discomfort.

We know not to eat moldy food because it can cause food poisoning, and aflatoxins even carry a cancer risk. However, many people remain unaware of the health hazards of a moldy house.

Decades ago, people discovered that staying in certain enclosed buildings, especially damp indoor environments, led to symptoms like headaches and breathing difficulties, which improved upon leaving the building. This is known as Sick Building Syndrome (SBS) [1].

Over the past decade or so, an increasing number of studies suggest that the mold accompanying dampness is not innocent. It can harm human health through three mechanisms: abnormal immune responses (such as allergies), direct infection, and toxic irritation from mold byproducts.

In 2004, the Institute of Medicine (IOM) found that indoor exposure to mold in healthy individuals is linked to upper respiratory tract symptoms, coughing, and wheezing [2]. Recent pathological studies indicate that spores and enzymes produced by mold can hijack lung cells and destroy cell connections, damaging the respiratory system [3, 4]. In summers with little pollen, mold is one of the primary triggers for allergies—causing annoying sneezing, runny noses, nasal congestion, coughing, itchy skin, and rashes.

Research shows that about 10% of people have IgE antibodies against common inhaled mold, meaning they are potentially allergic to it [5]. For asthma patients, mold can trigger asthma attacks; finding mold spots at home is never a good sign. In the US, it is estimated that up to 21% of asthma cases may be linked to damp and moldy residential housing [6].

Certain molds, like Aspergillus fumigatus, can also pose a deadly risk of lung infection to those with weaker immune systems, such as the elderly. Statistics from Peking Union Medical College Hospital on over 16,000 mold infection patients show that nearly half (49.3%) were aged 61 or older, with infections primarily occurring in the lower respiratory tract (e.g., lungs) (81.7%).

An October 2007 study in the American Journal of Public Health found that people living in damp, moldy environments have a 34% to 44% higher risk of depression compared to those in dry, mold-free homes. Allergies themselves can have a depressing effect—"a stuffy nose leads to a foggy brain" is a very real feeling for many allergy sufferers. Researchers suggest that repeated rhinitis, asthma, and headaches caused by mold may be linked to anxiety and depression [7].

01. Ventilation!

Dark, damp, and relatively enclosed environments are perfect for mold growth. Controlling air humidity is crucial; it's highly recommended to open windows frequently. Airflow helps regulate humidity and prevents the indoors from becoming too damp. As mold grows, it releases spores, fragments, and volatile organic compounds (VOCs) into the air. Ventilation exchanges indoor and outdoor air, diluting these risky substances. For areas with high overall humidity (like coastal regions), ventilation is still useful—you don't need to leave windows open all day; just enough to exchange the air.

Tip: If possible, use a dehumidifier or your AC's dehumidification function to help keep your home dry.

02. Find the Mold Hiding in Your Home

It's best to check materials prone to mold and hidden corners, such as:

1. Behind furniture and around crevices.

2. Inside air conditioning and exhaust systems.

3. Walls, wallpaper, and suspended ceilings.

4. Wooden cabinets and bed frames.

5. Clothes and books that haven't been touched in a long time.

6. Places that have previously leaked or been soaked in water.

(If you smell a musty odor when viewing a rental apartment, move on to the next one!)

03. Replace, Clean, and Disinfect Moldy Items

Throwing them away is the first choice—even dead mold fragments can still trigger allergies.

For things you can't throw away, disinfect, clean, and keep them dry. For mold removal, standard household bleach (like 84 disinfectant) is effective. Dilute it with water according to the instructions, wipe the moldy areas, wear gloves, and open windows for ventilation. Most commercial mold removers combine bleach with oxidizing agents (like hydrogen peroxide) and penetrants for a stronger effect.

1. For items that cannot be bleached (like shoes or books): clean them thoroughly and expose them to direct sunlight.

2. For moldy silicone sealant: use a mold removal gel; if the mold is severe, scrape off the old sealant and apply a new layer.

3. Regularly clean appliances that generate moisture, such as ACs and washing machines.

4. If you are renovating: prioritize moisture-proofing and mold-proofing technologies. Choose water-resistant materials, ensure smooth airflow, and thoroughly waterproof bathrooms, kitchens, sinks, and AC areas.

Reference:
[1]Park J H, Cox-Ganser J M. Mold exposure and respiratory health in damp indoor environments
[2] Basic Facts about Mold and Dampness
[3] Wiesner D L, Merkhofer R M, Ober C, et al. Club cell TRPV4 serves as a damage sensor driving lung allergic inflammation
[4] Jia L J, Rafiq M, Radosa L, et al. Aspergillus fumigatus hijacks human p11 to redirect fungal-containing phagosomes to non-degradative pathway
[5] Bush R K, Portnoy J M, Saxon A, et al. The medical effects of mold exposure
[6] 张丽,康梅,陈中举,et al.我国霉菌感染流行病学分析:多中心回顾性研究
[7] Shenassa E D, Daskalakis C, Liebhaber A, et al. Dampness and mold in the home and depression...
[8] WHO Guidelines for Indoor Air Quality: Dampness and Mould