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May 05, 2023

Can Mold Make You Sick? How to Keep Mold From Hurting Your Health

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Here's how mold can make you sick—and how to stay safe.

At first, Lauren Byington just felt tired, something she attributed to having a new baby. After a while, though, other symptoms appeared—yellowing skin, thinning hair, and pain in her liver, which made her think something was amiss. What that something was took Lauren, a 34-year-old entrepreneur in Bandera, TX, two years to discover. One doctor thought she might have Lyme disease; another worried that it could be cancer. Finally, allergy tests revealed that Lauren's symptoms were due to excessive exposure to mold.

Lauren had no idea where she’d been exposed to high levels of mold, so she combed her house for possible sources. She didn't find anything—no leaks under the sink, no cracks letting rain enter the walls, nothing dripping from the roof or the air conditioner. Then she remembered how her health worsened when she got into her touring van, a vehicle she used almost every month to drive her family nine hours to visit relatives; she and her kids would sleep in the van's two king-size beds. When Lauren stuck cotton swabs into the air vents and around the air conditioning unit in the roof of her van, they emerged black as night. Even though the van had been brand-new when her symptoms had first appeared, driving it from one climate to another on a regular basis had apparently led condensation to build up in the AC, allowing mold to grow. "I felt shocked, but there was also a sense of relief to finally know the source of my problems," Lauren says.

These fuzzy microorganisms are outside in the shade and where leaves and grass decompose, inside in the damp parts of our homes or offices, and even on some of the crops grown for our food. Mold spreads easily because the spores on the top of it readily float through the air.

Yet how much mold we’re each exposed to and exactly what harm it does is not well understood. "There's still quite a lot we don't know," admits Dori Germolec, Ph.D., a toxicologist at the National Institutes of Health (NIH). Part of the reason is that researchers can't ethically expose some people to mold and compare them with others they don't expose, following the method of the best clinical trials. Plus, there are thousands of species of mold and people tend to come into contact with a mixture of them along with bacteria and other organisms, so isolating one type of mold as the culprit behind specific symptoms is difficult. Scientists focus on monitoring how people are affected after floods, which does not provide comprehensive information.

What is clear is that too much mold is bad for our health. "When it's in excess, such as in a water-damaged building, it can become a problem, particularly for individuals with respiratory conditions such as asthma and allergies," Germolec says. More of us will experience this as climate change turbocharges storms and flooding as well as raises temperatures and humidity—all these things contribute to mold growth. Stachybotrys, the black mold in Lauren's van, produces toxins known as mycotoxins, as do others like it. But all kinds of molds can impact our health, according to a report on mold from the Institute of Medicine.

We can come into contact with mold in a variety of ways, none of them very.

Mold on our skin can cause redness or swelling. If it gets into cuts, it might form large warts or cauliflower-like lesions, notes the University of Florida Emerging Pathogens Institute. We can touch mold when we scrub the gunk off a bathroom shower or by picking up musty items stored in the garage without protective gloves, says Ryan Steele, D.O., an allergist- immunologist at Yale Medicine.

When it comes to hard cheese or firm fruits and veggies, you can cut away mold plus about an inch beyond it and eat the rest, the U.S. Department of Agriculture says. But if you see mold on other foods, such as bread and leftovers, in most cases you’ll need to toss the whole item, because contamination from mold branches and roots can run deep and you want to avoid accidentally eating mold. Some molds can be hard to see, so pay attention to food expiration dates and clean the inside of your fridge with water and baking soda every few months to keep mold from appearing.

This is the most common way we are exposed to molds, Germolec says. While we’re always breathing in some mold, it becomes an issue when we inhale an excessive amount over a prolonged period or when there's a big, sudden exposure, as might happen when we spend the day gardening and there's mold in the mulch, Dr. Steele says.

Researchers have carefully documented the ways mold can affect the respiratory system. It can cause an allergic reaction of sneezing, coughing, a sore throat, and a runny nose, and it can initiate or worsen asthma. A study of children living in New Orleans in the years following Hurricane Katrina, for example, found that kids in homes that sustained the most water damage were more likely than others to have decreased lung function. Other researchers estimate that across the U.S., children living with household mold are 45% more likely to have asthma than kids who aren't exposed. Mold-exacerbated asthma is especially prevalent in low-income neighborhoods, the NIH says; landlords in these areas may be less likely to remediate water leaks quickly. Finally, people who aren't asthmatic may still develop lung disease or infections when they are around mold, says Dr. Steele.

Those exposed to excessive mold complain of issues ranging well beyond the respiratory tract, such as headaches, fatigue, and brain fog, Germolec says. It was these three symptoms—along with skin rashes, body pain, and heart palpitations—that Megan Sherer, a 32-year-old hypnotherapist now in Seattle, experienced three years ago after she moved into a 100-year-old apartment building in New York City. Her issues started soon after she moved in, and she felt worse as the months went by. Nine months later, she contracted COVID-19, after which her health "completely collapsed," she says. "On an illness scale of 1 to 10, I was an 11." Though a naturally athletic person, she could barely take short walks, let alone hike, dance, or rock climb. She also stopped socializing with friends. Megan saw several health care professionals before a naturopath finally tested her for mold sensitivity as well as chronic Lyme disease. She came up positive for both—which, along with the COVID, the doctor thought, had overwhelmed her body.

Intrigued, Megan ordered a home test kit for mold that gave her special petri dishes she put around the apartment, then sealed and left in the dark. When she brought them out, she was stunned at what was growing in them. "You could see 10 different molds: black, green, red, and blue. It was pretty shocking and really gross," she says. As she was moving out, Megan found the source: cracks in a corner of a wall where outside water was getting in.

These days, Megan is feeling much better—integrative medicine treatments, including drugs, supplements, and light therapy, have significantly healed her. And it's helped that her new apartment is free of mold—she carefully tested it before moving in.

Not all doctors accept that such a wide array of symptoms can spring from mold exposure, says researcher Cheryl Harding, Ph.D., a professor emeritus of psychology at Hunter College, City University of New York. "Standard blood work doesn't show anything, so patients often get told it's all in their head" by skeptics, she says.

While it's true that high-quality studies on humans are largely lacking, animal research continues to document a wide range of harms from mold. In studies led by the National Institute for Occupational Safety and Health, the fungus Aspergillus fumigatus caused visible changes in the pulmonary arteries of mice. Additional studies are being conducted to assess possible cardiovascular effects.

Harding's animal studies have also found cognitive and emotional impacts: When mice were exposed to different mold spores, the animals exhibited brain inflammation and short- and long-term memory loss as well as increased sensitivity to pain. Some types of spores increased the mice's anxiety. Importantly, not every mouse had a significant reaction. "It's the same with people. They can be exposed to the same mold and have different symptoms or none at all, depending on their genes and other factors," Harding says.

Harding posits that in addition to causing respiratory harm, inhaling mold activates the immune system, leading to the release of cytokines, which results in inflammation in the brain and other organ systems. Such immune involvement could also explain why people with mold issues become more sensitive to mold over time—their immune systems have been primed by prior exposures, Harding says. She hopes other researchers continue studying immune responses to various mold stimuli in an effort to find more effective treatments.

Right now, doctors generally check for an allergic effect from mold using a skin-prick test. These tend to be limited to species of molds in a given geographic area, which means that if you move across the state or country and develop symptoms, you should be tested again. One way you can test whether your symptoms are caused by your environment is via a change of scenery: If symptoms disappear when you go away on vacation, your home or office could be the issue, Dr. Steele says. Treatments include antihistamine or steroid nasal sprays or oral medications as well as allergy shots to build up tolerance. "Relief from the shots happens within about six months, but it takes years to fully train the immune system to ignore the allergen," Dr. Steele notes.

It took two years for Lauren Byington to get over her mold symptoms, and she's careful not to reexpose herself. If a place smells even a tiny bit moldy, she walks away. "For two years it didn't cross my mind to consider mold," she says. "Now it's something I think about a lot."

Experts agree that the best approach is to prevent mold from growing in the first place. Here's how.

No one knows exactly how much mold or what species of it regularly live in our homes and offices. And there are no federal guidelines on how much mold is safe or unsafe, though many companies that do mold testing use levels designated by the Environmental Protection Agency for research purposes. But if you can see mold, there's no need to test for it, says Rubino. "If it's there, you want to remove it." Use a botanical cleaning product and microfiber towels, and wear protective gloves, an N95 mask, and eye protection to clean mold in an area that's 10 square feet or smaller. For larger spaces, call in a professional.

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