Just How Dangerous Is Mold?

Mold grows in almost any color, sprouts up year-round and can be found just about anywhere — spotting your shower curtain with fuzzy polka dots, cropping up in corners of your spooky basement and making itself at home in the siding on your house.

This funky fungus grows and thrives in damp, warm, humid places. And it can cause real problems for your health when it does.

How can you be exposed to mold?

Mold spores are teeny-tiny cells that spread through the air. They thrive in warm, damp, humid spots, both outdoors and indoors, especially anywhere affected by water damage (like leaks or flooding). When these spores land on things and start to reproduce, mold begins to grow.

“If you’re exposed to mold, you can develop breathing problems that range from mild to severe,” says critical care pulmonologist Lamia Ibrahim, MD. “To know how to protect yourself, start by knowing where mold spores thrive.”

Dr. Ibrahim shares some locations where mold is common (though this isn’t an exhaustive or complete list) and its potential impact.

Where mold grows outdoors

“Outside, you’ll find mold in shady, damp areas or where leaves or other vegetation break down,” Dr. Ibrahim says. This includes:

• The exterior of buildings, like the roof, deck and exterior windows and walls
• Garages and sheds
• Leaf and compost piles
• Wood piles, like tree stumps, rotting logs and stacks of firewood

Where mold grows indoors

“Inside homes and other buildings, mold grows in high-humidity locations, like basements and showers,” Dr. Ibrahim says, “and especially in areas where poor ventilation prevents water from drying quickly.”

Left a window open in a rainstorm and your carpet got soaked? Leaky toilet trickled through the living room ceiling? Haven’t checked inside your coffeepot since you bought it? Beware the high likelihood of mold.

Bathrooms are a common spot, too, even in the cleanest of homes. Mold can grow out in the open, like on shower curtains, shower walls and in holes in caulk and grout. But it can also lurk out of sight, like beneath loose tiles or in the toilet tank. (Check your toothbrush holder, too!)

Here are other places where mold is common:

• Air vents and ductwork
• Attics and crawlspaces
• Carpets and upholstery that have gotten wet
• Fireplaces and chimneys
• Heating and cooling appliances, like air conditioning units, water heaters, HVAC systems and humidifiers
• In the basement, especially in areas with leaks or flooding
• In the kitchen (for example, around the dishwasher, under the sink and in spots like your refrigerator drip pan and the water reservoir of your coffee pot)
• Inside the washing machine, like around the door and seal
• Inside mattresses
• On or beneath walls, floors and ceilings, including underneath paint and wallpaper
• Windowsills

This list sounds scary, we know. Like … is mold everywhere?! To some extent, yes: Mold is common, and many types of mold are generally harmless. But molds can also create toxins that can affect your health.

What happens if you inhale mold?

Breathing or touching mold can cause symptoms like allergic reactions, asthma and skin rashes. But which symptoms you experience depends on factors like your overall health, the strength of your immune system, your allergies, etc.

“Not everyone responds to mold exposure the same way,” Dr. Ibrahim clarifies. “Your symptoms may be different from other people’s, and they can range from mild to severe.”

She explains more about the possible symptoms of mold exposure.

Allergic symptoms

Mold spores produce allergens, or substances that can cause allergic reactions. Not everyone is allergic to mold, but if you are, you may experience symptoms like:

• Sneezing
• Skin rash
• Stuffy or runny nose
• Sore or itchy throat
• Headache

If you have a severe mold allergy, you can even develop fever, shortness of breath and anaphylaxis (a life-threatening allergic response).

Respiratory (breathing-related) symptoms

If mold exposure brings lasting allergic symptoms, you can develop a respiratory infection. Mold spores can also irritate your lungs and cause breathing troubles, even if you’re not allergic to mold.

“When they’re introduced to your body, spores irritate the airways in your nose, mouth and throat,” Dr. Ibrahim explains. This can cause:

• Coughing
• Chest tightness
• Shortness of breath
• Wheezing

Bleeding symptoms

“Mold spores can cause burning and bleeding if they become lodged in your mucus membranes, like in your sinuses and lungs,” Dr. Ibrahim warns. This may include:

• Bleeding gums
• Coughing up blood
• Nosebleeds
• Bleeding in your lungs

We’ll talk later about when to see a doctor for mold exposure, but it’s worth noting here: Bleeding symptoms always warrant a conversation with a healthcare provider.

Conditions caused by mold exposure

There are some specific conditions associated with mold exposure, like:

• Aspergillosis. This group of illnesses is caused by Aspergillus fungi. Symptoms are different for each type of aspergillosis but usually include infections or allergic reactions in your lungs.
• Hypersensitivity pneumonitis. This rare inflammatory lung disease brings coughing, breathing troubles and fever. It most often develops from mold exposure at work, but it can result from home exposure, too.
• Mycotoxicosis. Some types of mold produce dangerous mycotoxins, substances that can cause severe symptoms that include cancer and issues with your digestive system, immune system and nervous system. “It’s rare, but exposure to mold spores can eventually cause organ damage, cognitive difficulties and even death,” Dr. Ibrahim states.

Who is sensitive to mold?

If you’re feeling safe because you’ve never had breathing problems in the past, you may want to think again. In reality, mold can be responsible for breathing problems in almost anyone.

“There’s sufficient evidence to link mold exposure with upper respiratory tract symptoms like coughing and wheezing in otherwise healthy people,” Dr. Ibrahim says.

That said, certain conditions can make you more sensitive to mold:

• Allergies. If you already have environmental allergies (or a family history of them), you’re more likely to be affected by mold exposure.
• Asthma. Mold is linked to asthma symptoms in people who have asthma. Plus, about two-thirds of people with asthma also have environmental allergies.
• Other chronic conditions. Conditions that affect your lungs, like chronic obstructive pulmonary disease (COPD) and cystic fibrosis, may also make you more sensitive to mold’s effects.

Some people are at higher risk of developing breathing problems related to mold exposure, like:

• Children. Kids’ immune systems are still developing, so they’re especially vulnerable to mold. Research shows a link between household mold exposure and asthma in some children, especially if it already runs in the family.
• Older people. As you age, your lung function declines and your immune system weakens, which can make you more sensitive to mold. Seniors also often spend more time indoors, making the risk of mold exposure higher with age.
• People who are immunocompromised. If you have a weak immune system, like from a medical condition, treatment or medication, you may be at higher risk for symptoms related to mold exposure.

You’re also more likely to experience symptoms if you live or work somewhere where you’re regularly exposed to mold. But you might not even realize that’s the case.

“Pay close attention to symptoms that are only present or worsen at home or other public areas where mold is common,” Dr. Ibrahim advises.

How to minimize your risk of mold exposure

There’s no way to avoid mold entirely, but it’s best to avoid it as much as you can, especially if you know it gives you trouble.

“If you’re prone to breathing problems like asthma, try to limit your exposure to damp, humid areas like basements and saunas,” Dr. Ibrahim recommends.

To keep yourself and your family healthy, follow these tips for limiting mold exposure.

• Clean mold when you see it. Use mold-killing bathroom cleaning products, like bleach, to get ahead of the spread.
• Use an air conditioner or dehumidifier. “Keep humidity levels below 50% at all times,” Dr. Ibrahim advises. Humidity changes with temperature shifts, so check your home’s humidity level at least once a day.
• Turn on exhaust fans. Adequate ventilation can keep mold from growing and spreading. So, use exhaust fans (if you have them), especially when you shower.
• Remove or replace wet fabrics. Soaked-through carpets, rugs and upholstery are breeding grounds for mold spores, even if it happened in the past and they seem dry now.
• Replace carpeting, if you can. If possible, remove carpeting from your home and replace it with a surface that’s easier to clean, like tile.
• Buy paints fortified with mold inhibitors. Talk to an expert, like a mold assessor or painting contractor, about special paint that can offer protection from mold.

When to see a doctor

“For the most part, mold-induced breathing problems are temporary, and symptoms usually fade with less exposure to the fungus,” Dr. Ibrahim says.

But talk to a healthcare provider if you have symptoms of mold exposure, especially if you already have allergies or asthma. If you know you’ve been exposed to mold at home, at work or on a trip, tell them everything you can about the mold and the location.

“Be sure to mention all the symptoms you may have, no matter how trivial they may seem,” she stresses. “When you’re being evaluated for a new problem, there are no insignificant symptoms.”