Mold vs. Mildew: Here Are the Key Differences You Need to Know About

By: Diana Rodriguez-Zaba
Updated on: April 5, 2021

If you think that mildew and mold are the same thing, you’re almost right:

Mildew is a type of mold, but not all molds are mildew. The fungi thrive in moist environments, and they live on all kinds of surfaces, so they’re both housecleaning headaches.

While excessive mildew can cause health problems, it doesn’t have the toxic power of mold. Before you go after that splotch on the baseboard, you need to know the difference.

It is just plain mildew or something that needs attention from a mold remediation specialist?

You can answer that question with a little household bleach:

Just dab a few drops on the suspected area, and wait several minutes. If it becomes lighter, you’re dealing with mildew.

If it remains dark, you’re most likely dealing with mold (we’ll share some essential tips for DIY mold cleaning later on in the article).

Indoor Mildew Fungus

Ask a gardener about mildew, and you’ll get an accurate description of the fungus:

It’s a common problem on plants and vegetables, but mildew is a type of mold that can grow on any organic material inside your home. Paper, leather, wood, ceilings and floors are just a few of the surfaces that support this fungus.

Unlike mildew that grows outside, indoor mildew isn’t seasonal. As long as interiors stay warm, this type of fungus thrives inside the house. Even during the summer, you’d need to keep the thermostat set at or below 70 degrees Fahrenheit to put a chill on mildew growth.

Downy and powdery mildew on a grape leaf
Downy and powdery mildew on a grape leaf

These are the two most common types of mildew that you’ll find around the house:

1. Powdery Mildew

Identified by its white or gray color, this type of mold first appears as patterned splotches on surfaces, and it becomes yellow, black or brown as it grows.

2. Downy Mildew

Usually found on agricultural products, this mildew shows up in your home as a yellow surface-growing fungus that eventually turns brown.

The 4 Most Common Mold Types

According to CDC estimates, the number of mold species exceeds 10,000 and may be as high as 300,000. This type of fungus is hardier than mildew because it grows in temperatures ranging from 40 to 100 degrees Fahrenheit. 

The fuzzy or slimy growth is usually black or green, but its color can appear as shades of white mold, blue, gray, brown and yellow.

Mold also grows deep into organic materials around the house. Left undetected, mold spreads behind walls, into subflooring and through ceiling joists. Over time, mold damage can compromise your home’s structural integrity.

There are many warning signs of mold in your home; be sure to familiarize yourself with them.

Airborne mold spores are associated with a wide variety of health issues. Stachybotrys, also called toxic black mold, is especially dangerous, and we’ll cover it in more detail with a future post.

Most household molds are one of these 4 types:

1) Alternaria

alternaria mold in bathroom

This mold is dark brown and has a wooly or down-like texture.

Alternaria is one of the few molds that can also thrive in environments with very little moisture like bedding, upholstery and insulation.

2) Cladosporium

green black mold cladosporium

There are more than 30 species of this mold, and 22 are known to cause health problems.

Cladosporium is identified by its powdery appearance and black or olive green color.


3) Penicillium

mold penicillium on wallboard

You’ll find this mold growing on stale bread or old cheese, but it also takes hold in mattresses, carpets and even wallpaper.

The fuzzy green or blue fungus is used to produce penicillin and commonly produces a strong musty odor.

4) Stachybotrys

black mold stachybotrys

Of all the mold types, this slimy fungus is the most likely to threaten your family’s health. Toxic black mold gives off a noticeable musty smell and grows rapidly in areas that are constantly damp.

A water leak behind a wall can breed mold quickly, and wet basements are often affected by mold as well.

Tips for Preventing Mold and Mildew

Now that you know mold and mildew a little better, let’s look at easy ways to keep the fungi from taking over your home. These tips can make a big difference.

  • Keep moisture levels below 60% by running dehumidifiers.
  • Don’t let wet towels hang around in bathrooms.
  • Don’t let damp clothes pile up in the laundry room.
  • Ventilate cabinets by leaving doors open once a week.
  • Improve interior air flow by positioning furniture away from walls.
  • Keeping up with basement maintenance keeps the downstairs dry.

Important DIY Precautions

We outlined the seven steps for DIY mold cleanup projects in this post. If you’re thinking about taking on the job yourself, be sure to follow our recommended precautions.

DIY mold removal can have very negative effects on your health, so always be cautious.

Never attempt to do it yourself if:

  • The area that’s affected covers more than 3 square feet.
  • The material or surface is difficult to clean.
  • You suffer from any type of respiratory problem.

Advantages of Professional Mold Inspection Services

mold inspection expert

Unlike ordinary mildew with its flat growing patterns, molds attach to materials with microscopic filaments that penetrate beneath surfaces. Its invasive growth quickly spreads through sheetrock and wood causing permanent damage to your home’s structure.

It’s hard to tackle mold with DIY remedies because the fungus grows in areas that you can’t see or access.

The safest way to determine the extent of a mold problem is to call in a company that handles inspections and mold testing here in Chicago, IL or your area.

A mold remediation contractor determines the type of mold in your home, its location throughout the house and the best course of action for addressing its source.

Professional mold removal services are often the safest way to eliminate this potentially dangerous problem.

Dealing with Mold in the Chicago area? We Can Help!

By recognizing the difference between mold and mildew, you can make a better decision about cleaning strategies.

It’s important to always remember that DIY mold cleanup requires special precautions, so be careful before starting a project by yourself.

If you aren’t sure about the best course of action, ServiceMaster Restoration by Zaba offers inspections, testing and mold removal services for Chicago homes and businesses.

We want you to be safe, so just give us a call: 773-647-1985

How are mildew and mold different?

Mildew is a type of mold. However, not all molds are mildew. Mold grows on and into porous, organic materials. Mildew lives on hard surfaces like bathroom tile. Mildew is powdery and lighter in color than other molds.

Which is worse, mold or mildew?

Mold is more invasive than mildew. It grows quickly in drywall, wood and carpet making it very difficult to remove. Mildew doesn’t penetrate surfaces, so it’s easier to eliminate.

Is mildew harmful to your health?

Mildew exposure can cause the same symptoms as mold exposure. Both microorganisms spread as airborne spores, so both are easily inhaled. Mildew allergy symptoms include congestion, watery eyes and respiratory problems.