Mold at Home: Signs, Health Effects and How to Get Rid of It Safely

It starts small. A musty smell in the bathroom you can't quite place. A few black specks on the windowsill. A gray shadow creeping across the corner of the ceiling above the shower. Then one day you move a dresser away from the wall and find a fuzzy patch that makes you take a big step back.

Mold is one of the most common problems in homes, and one of the most misunderstood. Some people panic at the first sign of it, while others ignore it for years. The truth sits in the middle: mold is fixable, and the real key isn't the mold itself. It's moisture.

What is mold?

Mold is a type of fungus that grows in damp places. Tiny mold spores float in the air almost everywhere, indoors and out. They only start growing into visible mold when they land on a surface that's damp enough and has something to feed on, like wood, drywall, fabric, paper, dust or soap scum.

That's why you can't get rid of mold spores completely, and you don't need to. What you can control is moisture, which stops mold from taking hold.

Signs of mold in your house

Mold isn't always obvious. Look and sniff for:

• Visible growth: black, green, gray, white or even orange spots or fuzzy patches
• A musty, earthy smell, especially in basements, closets or bathrooms
• Water stains or discoloration on ceilings and walls
• Peeling, bubbling or cracking paint or wallpaper
• Warped wood or soft drywall
• Condensation that regularly forms on windows or pipes
• Allergy symptoms that improve when you leave home

Common places to check include bathrooms, under sinks, around windows, basements, attics, laundry rooms, behind furniture against outside walls, and around air conditioning units.

Health effects of mold exposure

Not everyone reacts to mold, but for some people it can cause real problems. According to the CDC, exposure to damp and moldy environments can cause:

• Stuffy nose
• Sneezing
• Wheezing or coughing
• Red or itchy eyes
• Itchy skin or rash
• Sore throat

People more likely to have stronger reactions include those with:

• Mold allergies
• Asthma, which mold can trigger or worsen
• Chronic lung conditions
• Weakened immune systems, who can be at risk of serious mold infections

The term "toxic black mold" gets thrown around a lot. Some molds, including the one often called black mold (Stachybotrys chartarum), can produce substances called mycotoxins. But the CDC notes that the color of mold doesn't tell you how dangerous it is, and all mold should be cleaned up and the moisture problem fixed. There's also a lot of misinformation online linking mold to a wide range of illnesses. If you think mold is affecting your health, talk to a doctor rather than relying on social media claims or unproven "mold detox" products.

What causes mold?

Mold needs moisture. Common causes include:

• Leaks: from roofs, pipes, windows or appliances
• High humidity: especially in summer or in poorly ventilated rooms
• Condensation: on cold windows, walls and pipes
• Poor ventilation: in bathrooms, kitchens and laundry rooms
• Flooding or water damage
• Drying clothes indoors without ventilation
• Damp basements and crawl spaces

How to get rid of mold safely

First: fix the moisture problem

Cleaning mold without fixing the source of moisture is like mopping up a leak without turning off the tap. It'll come back. Repair leaks, improve ventilation and dry wet areas within 24 to 48 hours where possible.

When you can clean it yourself

The EPA suggests that if the moldy area is less than about 10 square feet (roughly a 3-foot by 3-foot patch), you can usually clean it yourself. For larger areas, or if mold is in your heating and cooling system, consider calling a professional.

Protect yourself

When cleaning mold:

• Wear gloves, goggles and an N95 mask
• Open windows and run a fan to ventilate
• Keep kids and pets out of the area
• If you have asthma, allergies or a weakened immune system, ask someone else to do it

How to clean mold from hard surfaces

1. Scrub the mold off with detergent and water.
2. Dry the surface completely.
3. For stubborn spots on hard, non-porous surfaces like tile or glass, some people use a diluted bleach solution. The CDC suggests no more than 1 cup of household bleach per gallon of water.
4. Never mix bleach with ammonia or other household cleaners, which can create toxic gases.

What to throw away

Porous materials like ceiling tiles, carpet, insulation and drywall that have become moldy may need to be removed and replaced, since mold can grow deep inside them. Moldy fabric items may be salvageable with a hot wash, but heavily affected items are often best thrown out.

When to call a professional

Get professional help if:

• The moldy area is larger than about 10 square feet
• There's been significant water damage or flooding
• Mold is in your heating, ventilation or air conditioning system
• You smell mold but can't find it, since it may be inside walls
• You're a renter, in which case contact your landlord first

How to prevent mold

Keep humidity in check

The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. A cheap hygrometer can tell you your home's humidity. If it's high:

• Use a dehumidifier, especially in basements
• Run air conditioning in humid weather
• Ventilate rooms where moisture builds up

Ventilate bathrooms and kitchens

• Run the bathroom exhaust fan during showers and for at least 20 to 30 minutes after
• Use the kitchen range hood when cooking
• Crack a window if you don't have a fan

Deal with condensation

• Wipe condensation off windows in the morning
• Keep furniture a few inches away from outside walls so air can circulate
• Insulate cold pipes

Dry things quickly

• Fix leaks as soon as you notice them
• Dry spills and wet areas within 24 to 48 hours
• Don't leave wet laundry sitting in the washer
• Dry clothes outside or use a vented dryer when you can

Keep it clean

• Clean bathrooms regularly to remove soap scum, which mold feeds on
• Wash shower curtains and bath mats
• Empty and clean dehumidifier tanks and drip trays
• Check under sinks regularly for leaks

Mold and renters

If you rent, mold can be tricky. In many places, landlords are responsible for repairs that cause mold, like leaks and broken ventilation. Steps to take:

• Report it to your landlord in writing, with photos
• Keep copies of all communication
• Check your local tenant rights resources and housing codes
• Do what you can to reduce humidity in the meantime

Mold, your home and your wellbeing

Living in a damp, moldy home can affect more than your lungs. It can be stressful, embarrassing and exhausting to deal with. Taking steps to fix it, one at a time, can make your home feel healthier and calmer. Our guides to a healthy home environment and whether air purifiers work have more ideas for improving your indoor air.

A quick monthly mold check

Preventing mold is much easier than removing it. Once a month, take five minutes to check:

• Under kitchen and bathroom sinks for drips
• Around the base of the toilet and the edges of the tub and shower
• Window frames and sills for condensation and dark spots
• Behind and under appliances like the washing machine and fridge
• Basement corners and walls
• Air conditioning units and drip trays

Catching a small leak early can save you a big repair bill and a lot of stress later.

Frequently asked questions

Is mold in my house dangerous?

Mold can cause allergy-like symptoms and trigger asthma, and it can be more serious for people with weakened immune systems. All mold should be cleaned up and the moisture source fixed.

Is black mold more dangerous than other mold?

Not necessarily. The CDC says the color of mold doesn't determine how hazardous it is. Treat all mold the same way: clean it and fix the moisture.

Can I clean mold with vinegar?

Some people use vinegar on small areas, but scrubbing with detergent and water and drying thoroughly is the main recommended approach. The most important step is fixing the moisture problem.

What humidity level prevents mold?

The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent.

When should I call a mold professional?

Call a professional if the mold covers more than about 10 square feet, if there's been significant water damage, or if mold is in your heating and cooling system.

A healthy home supports a healthy you. Take our free wellness wheel quiz to see how your environmental wellness is doing.