Mold vs. Mildew: How to Tell the Difference

Mold vs. mildew comes down to this: mildew is a kind of mold. The EPA says "mildew" refers to certain kinds of mold or fungus and is often used for mold growth that stays flat on a surface, such as on shower walls and window sills. In everyday terms, mildew is usually a thin, powdery, white, gray or yellowish surface growth that wipes off, while the growth people call "mold" is often fuzzy, darker, and can grow into the material underneath.

Both need moisture, both can trigger allergies in sensitive people, and both come back if the dampness is not fixed. The difference that matters most to a homeowner is depth: surface growth on a hard surface is a cleaning job, while growth inside drywall, wood or carpet is a removal job.

Mold vs. mildew at a glance

These visual clues are a guide, not a test. You cannot identify a mold species by looking at it, and the CDC says it is not necessary to know the type: all indoor molds should be treated the same way for health risk and removal.

How to tell the difference at home

Use a simple three-part check:

1. Look at the texture. Flat and powdery points toward mildew. Fuzzy or raised growth points toward mold.
2. Check the surface. Growth on tile, glass, painted trim or a plastic shower liner is usually surface growth. Growth on drywall, unsealed wood, carpet or ceiling tiles may go deeper.
3. Test the wipe. Wearing gloves, wipe a small spot with a damp cloth and a household cleaner. If it comes off and stays gone, it was surface growth. If it stains, returns within days, or the material underneath is soft, crumbly or discolored, treat it as mold in the material.

Also look for the water source. Mildew and mold both point to a moisture problem, whether that is a steamy bathroom, condensation on a cold window or a slow leak. Our guide to signs of water damage can help you trace it.

How do you know if there's mold or mildew in your house?

Often the nose finds it first. Watch for:

• A musty smell, especially in closets, basements, crawl spaces and bathrooms
• Spots on grout, caulk, window frames or shower curtains
• Discolored or peeling paint, or stains on ceilings and walls
• Mildew spots on stored clothes, leather or books
• Fogged windows and damp sills from condensation

The EPA notes that mold can hide on the back of drywall, wallpaper and paneling, the top of ceiling tiles and under carpet, so a smell with no visible source is worth investigating.

Mold vs. mildew smell

Both have a musty, earthy odor. The University of Missouri Extension notes that mold leaves a musty odor on what it grows on (Missouri Extension), and the EPA says mold in unventilated areas like basements can produce a strong musty smell. The EPA explains that some of these odors come from chemicals molds give off, called microbial volatile organic compounds (mVOCs).

Smell alone cannot tell you which one you have. A strong or lasting musty odor, especially one that returns after cleaning, suggests more growth than you can see.

Where mildew and mold grow

The University of Missouri Extension says mildew thrives in damp, warm, poorly lit places with little air movement, like cellars, crawl spaces and closets, and is most common in humid summer weather in closed-up houses. It commonly damages cotton, linen, rayon, silk, wool, leather, wood and paper.

Mold that people worry about in a house is most often on materials that got wet and stayed wet: drywall after a leak, subfloors after a flood, insulation in a damp attic. The EPA advises drying water-damaged areas and items within 24 to 48 hours to prevent mold growth.

Are mold and mildew harmful?

Both can affect health in people who are sensitive. The EPA says molds can cause allergic reactions such as sneezing, runny nose, red eyes and skin rash, can trigger asthma attacks in people with asthma, and can irritate the eyes, skin, nose, throat and lungs. The CDC says people with asthma, mold allergies, weakened immune systems or chronic lung disease may have stronger reactions.

Calling something "mildew" does not make it harmless, and calling it "mold" does not make it dangerous. Amount, location and who lives in the home matter more than the label. See a doctor if you have symptoms. Our guide to mold exposure symptoms covers what health agencies say.

How to remove mold and mildew

Step 1: Fix the moisture

The EPA's basic rule is that "the key to mold control is moisture control." Run the bathroom fan during and after showers, fix drips, and keep indoor humidity no higher than 50%, as the CDC recommends.

Step 2: Clean hard surfaces

1. Open a window or run a fan.
2. Wear gloves and goggles. The EPA recommends an N-95 respirator for mold cleanup.
3. Scrub with detergent and water, which the EPA recommends for hard surfaces.
4. For stubborn spots, the CDC allows a bleach solution of no more than 1 cup of household laundry bleach per gallon of water.
5. Rinse and dry completely.

Never mix bleach with ammonia, vinegar or other cleaners. Poison Control warns that bleach and vinegar together release chlorine gas. If you are curious about vinegar as a cleaner, see does vinegar kill mold.

Mold and mildew stain removers. Store-bought products labeled for mold and mildew can help with surface stains. Follow the label exactly, ventilate, and do not combine products. A stain that keeps coming back usually means moisture or growth behind the surface.

Remove mold and mildew from the shower

Shower walls are the classic mildew spot. Scrub tile and grout, wash or replace plastic liners, and dry surfaces after use. The University of Missouri Extension suggests stretching out wet shower curtains so they dry. If caulk is stained deep inside, it is often simpler to cut it out and recaulk once the area is dry. Our guide to mold in the shower and bathroom has more detail.

Remove mold and mildew from wood

For mildew on wood, the University of Missouri Extension advises drying the wood with heat and air circulation, scrubbing with a cleaning solution, rinsing and drying, and replacing badly affected wood (Missouri Extension). Wood that is soft, crumbling or has growth that returns needs a closer look. See mold on carpet and wood.

Mildew on clothes and fabric

The main practical difference between mildew and mold on clothes is how much damage has been done. The University of Missouri Extension notes mildew can discolor fabric and, over time, rot it. Its advice: act quickly, brush off growth outdoors, wash with detergent, and dry in the sun. For remaining stains on bleach-safe fabrics it suggests 2 tablespoons of chlorine bleach per quart of warm water for 5 to 15 minutes, then rinse; never use chlorine bleach on silk, wool or spandex. Fabric that is weakened or falling apart should be thrown away.

When to call a professional

The EPA says an area under about 10 square feet can usually be cleaned by a homeowner. Consider professional mildew or mold remediation when:

• Growth covers more than about 10 square feet
• It is on or inside drywall, insulation, carpet or ceiling tiles (the EPA says porous items may need to be thrown away)
• It followed a flood, sewage backup or major leak
• You suspect mold in the HVAC system (the EPA says not to run a system you suspect is contaminated)
• Someone in the home has asthma, allergies or a weakened immune system

If the growth came from a leak or flood, the structure needs to be dried properly too. Our mold remediation and water damage restoration guides explain the process.

Getting local help

Flood Rescue Pros is a free service that connects homeowners with independent local water damage and mold restoration companies. If the problem is bigger than a surface wipe-down, you can get help now or check service areas.

Frequently asked questions

Is mildew a type of mold?

Yes. The EPA says mildew refers to certain kinds of mold or fungus, and the word is often used for mold that grows flat on a surface.

What does mildew smell like?

Mildew has a musty, damp, earthy smell, much like mold. Smell cannot tell the two apart, and a lasting musty odor is a sign to look for hidden growth.

What kills mold and mildew?

For hard surfaces, the EPA recommends scrubbing with detergent and water and drying completely, and the CDC allows a bleach solution of no more than 1 cup per gallon of water. Porous materials with mold usually need to be removed, and the moisture source has to be fixed.

What is the main difference between mildew and mold on clothes?

Mildew on clothes is usually a surface stain that can often be washed out if caught early. The longer it stays, the more it can discolor and weaken fabric, and badly damaged items should be discarded.

Is mildew less harmful than mold?

Not necessarily. Health agencies do not separate the two. Both can cause allergy symptoms and trigger asthma in sensitive people, so clean up either one and fix the moisture.

Key facts

• Mildew is a kind of mold; the EPA says the term usually means flat surface growth in damp spots like shower walls and window sills.
• Mildew tends to be flat and powdery; "mold" is often fuzzy and may grow into porous materials.
• You cannot identify mold type by looks, and the CDC says all indoor molds should be treated the same way.
• Both can cause allergy symptoms and trigger asthma in sensitive people.
• Clean hard surfaces with detergent and water; keep humidity at or below 50%; dry wet materials within 24 to 48 hours.
• Growth over about 10 square feet, or inside drywall, carpet or insulation, calls for professional help.