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Mold vs. Mildew: What’s the Difference?

Marc McCollough

By Marc McCollough
Published August 7, 2023

You might use the terms mold and mildew interchangeably or you might combine them in a single phrase to describe fungi. While similar, the terms mold and mildew have different meanings. Learn what mold is, what mildew is and get tips on identifying, preventing and removing these types of fungi.

A yellow rubber duck on a bathtub next to a wet blue tile wall with moldy grout.

What is Mold?

Mold growing on a white wall under a window with brown wood trim.

The term mold refers to microscopic fungi in general. There are thousands of types of mold. Many don’t present a problem to people, but some can create issues ranging from simple discomfort to more serious health issues. In some cases, some types of mold can damage your home and property.

What Does Mold Look Like?

Mold generally is dark, with a black, blue, green or red color. It may appear fuzzy or slimy.

Mold grows downward into a surface and may grow upward as well. Subsurface growth makes it somewhat difficult to remove mold completely and can also cause damage to the material it grows on.

What is Mildew?

A person wearing cleaning gloves wiping mildew off of a black leather chair with a yellow towel.

Mildew is a specific type of mold. It has a growth habit and appearance that distinguishes it from other types of mold. Its odor is also a bit different — it’s generally not as strong as that of other types of mold.

Good to Know

All types of mildew are mold, but not all types of mold are mildew.

What Does Mildew Look Like?

Mildew begins with a gray or white color but it can turn brown over time. It has a powdery, flat appearance unlike other types of mold. Mildew typically grows outward and remains on the surface of a material, so it’s easier to remove than other types of mold and has less potential for damage. While mildew can grow on textured materials, you’re more likely to find it growing on flat, smooth surfaces.

Mildew and Mold Similarities

In spite of the differences in appearance and growth, both mold and mildew are types of fungi, organisms that consume organic material and that reproduce by means of spores.

There are other similarities as well:

  • Their spores can germinate within a couple of days.
  • They can grow in areas with excessive moisture.
  • They grow best at temperatures ranging from 60 to 80 degrees Fahrenheit.
  • They grow on drywall, wood, fabric, leather, painted surfaces and more.
  • They can damage your home or property.
  • They can cause health problems.
  • They typically have a distinct, earthy odor.

Mold and Mildew Growth

A close-up of mold growing on grout between a bathtub and a tile wall.

Mold and the type of mold known as mildew can grow quickly in the right conditions. Mold and mildew spores are very common in indoor and outdoor air and once they land on a surface, the conditions the mold or mildew needs to develop and thrive are relatively basic. They need moisture and oxygen and the food provided by organic materials. They also need the right temperature range, but that range — between 60 and 70 degrees Fahrenheit — can be common for many living spaces in a home.

The Best Conditions for Mold and Mildew

Factors that make an area or surface especially vulnerable to fungal growth include:

  • Excessive moisture
  • Darkness
  • Poor ventilation
  • Clutter, dirt and other debris

Where Do Mold and Mildew Grow?

Where are you likely to find mold and mildew? You may discover these fungi in several areas in and around the home:

  • Near a tub or shower, on the walls and on tile grout
  • Areas around heating/air conditioning registers where moisture can condense
  • On walls near windows as a result of leaks
  • On window glass and frames as a result of excessive condensation
  • On floors, walls or cabinets around leaky pipes
  • On ceiling joists, ceiling panels or drywall near a roof leak
  • On or under carpet and on or inside walls after a leak or flooding
  • In basements or crawlspaces with flooding problems, poor ventilation or excessive moisture

Health Risks From Mold and Mildew

Many types of mold, including mildew, can cause respiratory issues and allergic reactions. You may notice the symptoms right after touching the fungi or inhaling the spores or the effects may occur later. Effects can include:

  • Sneezing
  • Red, irritated eyes
  • A sore throat
  • A runny nose
  • A rash
  • Body aches

These fungi can also be a particular cause of concern for individuals who suffer from asthma; they can set off asthmatic episodes, including shortness of breath, wheezing and coughing. Mold may also lead to respiratory infections in people with weakened immune systems.

Mold and Mildew Damage

Damaged, peeling drywall on a moldy wall next to a window.

Some types of mold can cause physical damage in a home once it becomes established on a surface made of organic material. Mold that grows on and into surfaces such as paper and wood breaks down the organic components and consumes them. Mold can stain drywall and grout and cause drywall and some types of insulation to deteriorate. Left untreated, it can begin breaking down wood studs and joists and lead to serious structural damage to a home.

Mildew can also cause damage, but since it grows only on the surface of a material and is easier to remove, mildew damage is more likely to be cosmetic.

How Do You Prevent Mold and Mildew?

Mold and mildew grow easily in the right environment, but simply keeping your home clean is a good first step in preventing them from becoming established. Clutter, dirt, dust and debris can hold moisture and give mold a good place to develop. Excessive clutter can also hide mold growth, allowing it to become a serious problem before you notice it.

In addition to maintaining a clean home, there are some steps you can take to protect your home from mold and mildew:

  • Address a leaking roof, leaking pipe, leaking toilet, leaking window, etc. as soon as you notice it. Repairs may be simple do-it-yourself projects or you may need to hire a professional.
  • Maintain a humidity level between 30% and 50% in your home. Use humidifiers if needed.
  • Avoid closing up damp clothing, towels, dishcloths, etc. in a hamper or storage bin. Let them dry fully first.
  • Don’t let wet clothes remain in a washer. Remove them and dry them as soon as possible.
  • Spread out your shower curtain after using the shower.
  • Use a bathroom exhaust fan when showering or bathing.
  • If you have a ducted range hood — one that vents to the home exterior — use it when cooking and washing dishes.
  • Make sure your dryer vent is clear and working correctly.
  • Control water and moisture in your basement.
  • Maintain good ventilation in your home. Even if you can’t keep the windows open, a well-maintained heating, ventilation and air conditioning (HVAC) system will help circulate the air. You can even find HVAC filters designed to capture mold spores.
  • Consider using moisture absorbers in areas with excess moisture. However, make sure you promptly locate and address any underlying problem that’s creating the moisture issue.

Take a look at our guides to controlling moisture and humidity and preventing mold and water damage for more ideas on minimizing conditions that encourage mold and mildew growth.

How to Get Rid of Mold and Mildew

Before trying to clean mold or mildew from a surface, make sure you’ve addressed the moisture problem that led to the mold or mildew growth. Once you’ve corrected the problem and the area is completely dry, cleanup can begin.

Small Mold and Mildew Cleanups

According to the Environmental Protection Agency (EPA), homeowners can often handle a small mold cleanup job (an area smaller than about 10 square feet), but if you’re not comfortable with the project, call a professional.

If you decide to clean a small area yourself, you’ll need an N95 respirator, cleaning gloves and safety goggles. You’ll also need good ventilation.

  • In many cases, you can remove mold and mildew from hard surfaces such as windows, tile and walls with a scrub brush and a mold remover or an appropriate household cleaner. Our guide to cleaning mold from hard surfaces will give you some general cleaning steps.
  • If mold is growing into a porous surface, you may not be able to clean it enough to remove the mold entirely. You may need to replace moldy carpet or upholstery, for example.
Caution

Follow the manufacturer's use and safety instructions for any cleaning product.

Large Mold and Mildew Cleanups

For areas larger than 10 square feet, multiple areas of mold growth, or if you’re simply not comfortable doing the cleanup yourself, contact a professional.

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