Mold and Mildew

Mold vs. Mildew: The Main Differences & How to Tell Them Apart

Mold and mildew are often used interchangeably in casual conversation, but these two pesky fungi are quite different in both characteristics and effects. 

What is mildew and what is mold? What is the difference between mold and mildew? What does mold look like and what does mildew look like? In this blog we will discuss these questions and more including the effects of mildew and mold on your home and your health. 

An Introduction to Mold and Mildew

Mold and mildew are common fungi commonly found in homes in some capacity. It is commonly understood that mold and mildew thrive in moist environments and live on various surfaces throughout the home, but what is mildew and mold really

What is Mildew?

Mildew is a fungi that grows on various surfaces, and is less invasive than its mold counterparts. There are two major categories of mildew: powdery mildew and downy mildew. 

Mildew Type: Powdery Mildew

Mildew can affect any flowering plant.

Powdery mildew is a type of mildew that affects any flowering plant. Powdery mildew is identifiable by its white, grey splotches, which may turn yellow or brown over time as the mildew grows.

Mildew Type: Downy Mildew

Downy mildew is another type of mildew that affects agricultural products. Downy mildew can vary in visual appearance depending on the surface where it grows, however, this type of mildew is often spotted yellow that eventually turns brown over time. 

What is Mold?

Mold is also a fungi that grows on various, moist surfaces. Mold spreads by producing small reproductive cells referred to as “spores” that travel through the air and land on surfaces. The most common types of mold are: alternaria, aspergillus, cladosporium, penicillium, and stachybotrys chartarum. 

Mold Type: Alternaria

Alternaria is mold that is often found on consistently damp surfaces including windows, under sinks, in showers, or in buildings with water damage. Alternaria mold will appear black, dark brown, or grey with a fuzzy texture that closely resembles wool. 

Mold Type: Aspergillus

Aspergillus mold is frequently found in the home, more specifically on walls, insulation, on paper products, or on clothing material. It can appear in various colors including black, grey, brown, green, yellow, or white.

Mold Type: Cladosporium 

Cladosporium is a mold type that appears on various fabrics including carpets and curtains. Cladosporium can also be found on wood surfaces including cabinets and floorboards. This type of mold is generally black or olive.  

Mold Type: Penicillium

Penicillium mold is found on surfaces or in spaces that have frequently been in direct contact with water including mattresses, wallpaper, and home insulation. This mold is easily spreadable, smelly and commonly identified by its green or bluish color. 

Mold Type: Stachybotrys chartarum

Stachybotrys chartarum or “black mold” is the most dangerous type of household mold. This type of mold is black, smells musty, and can produce toxic compounds that pose a health hazard.  

The Difference Between Mold and Mildew

Let’s say you have identified a substance on a surface in your household that is clearly either mold or mildew. How can you tell the difference between mold and mildew

Mold and mildew can be differentiated by 3 key features: appearance, smell, and location. 


The difference in appearance between mold and mildew.

What does mold look like? Mold looks either fuzzy or slimy with irregular shaped spots that can vary in color between black, grey, brown, green, yellow, blue, or white. Surfaces on which mold has grown may begin to rot. 

What does mildew look like? Mildew is generally grey or white with a powdery appearance. Mildew grows in splotches or streaks and can change color to a brown or black color over time. 


While both mold and mildew can smell unpleasant, each fungus has a distinctive smell. Mildew has a musty smell, think your kid’s soggy sports gear, while mold has a rotting smell. 


If color and smell are coming up with more questions than answers, you can easily identify the difference between mold and mildew by the location of the fungus. Mildew most often grows on various surfaces while mold often grows under various surfaces including under countertops, behind vents, and in corners or cracks. 

The Effects of Mildew and Mold

The effects of mildew and mold are significantly different with mildew producing less severe effects than its mold counterpart. Despite this fact, it is best to treat mildew and mold in the early stages if possible to avoid any damage to your home. 

The Effects of Mildew

The effects of mildew is a mild allergic response.

The effects of mildew are generally mild and will not permanently damage your home surfaces. 

If mildew is inhaled, it may trigger allergy symptoms, respiratory irritation, headache, cough, or coughing. If mildew is consumed through unwashed food and crops, it may cause respiratory conditions and mild allergic reactions.

The Effects of Mold

The effects of mold are far more significant than the effects of mildew. Mold can damage your home surfaces, causing rot and potentially damaging the structure of your home. 

Exposure to mold can cause a variety of health conditions. If inhaled, mold can trigger an asthma attack, allergy symptoms, respiratory problems, joint pain, fatigue, dizziness, heart problems, and more. Exposure to black mold can cause long-term effects on those with weakened immune systems including children, those who suffer from respiratory conditions, and individuals with auto-immune diseases. 

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