Mold Vs Mildew: What Are The Differences? Plus Black Mold, Health Risks, And More

When it comes to the difference between mold and mildew, there’s a lot of confusion out there. Many people think of mold or mildew as “that stuff that you get if your walls get wet.”

The truth is actually far more serious! In fact, mold is a health hazard that can cause long-term damage to both you and your home.

But what is the difference between mold and mildew? How can you tell the differences between black mold vs mildew? Read on to learn more!

Infographic – Differences between mold and mildew

Mold vs mildew difference facts infographic guide

What is the difference between mold and mildew?

Image showing a mold vs mildew comparisonImage showing some of the ways you can tell the difference between mold vs mildew. Both grow when conditions are right (I’ll cover that in detail later) and are types of fungi. However, mold grows differently (often in roundish patterns) and rises further above a surface. Mildew has a flat surface, is often slimy or greenish-black in appearance, and tends to grow in a shape more resembling a spill.

Just want a quick answer to the question? Here’s a quick summary of the difference between the two.

How to tell mold vs mildew
  • The easiest way to distinguish mold from mildew is their appearance: Mildew grows with a flat appearance and outward in a pattern along small crevices (like between bathroom tiles), often with a shape resembling a large dark spill. It’s often greenish-black or slimy in appearance. Mold often grows in a pattern with many small circles and has a slightly fuzzy appearance, rising above the surface it grows on.
  • Both are found in different colors and shades, especially as they continue growing as the color may change as time goes by.
  • They’re both microscopic fungi and many variations exist. Both grow when the right combination of temperature & moisture/wet surfaces exist. Both grow where organic material can supply them.
  • Mildew typically does far less damage and is easier to get rid of than mold. Often a good cleaner and a bit of scrubbing are all you need. However, mold causes permanent damage to the materials it grows on and often requires replacement. You may need professional service to safely handle mold damage.
  • Both can produce spores you may inhale, and some molds produce mycotoxins (toxins they release). This can lead to serious health problems, especially respiratory.

Long story short, the easiest way to tell the difference is in how they look. Many people have a tendency to confuse the two so it’s helpful to understand how they’re different.

Both do have a few similarities in that they’re fungi and start growing under similar conditions and where spores are present.

Where they like to grow

Basically, both can grow quickly in moist, warm places. However, each type seems to have a preference when it comes to where they start growing.

In fact, it’s not just how they’re different you need to know, but also why they’re a health hazard you should take seriously. Additionally, mold can do permanent, expensive damage that costs a lot of money to repair!

I’ll explain more as we go.

What is mold?

Mold growth indoors on walls (image colors edited to make the mold easier to see). Where water dampens materials inside homes and buildings, and the temperature is ideal (warm), spores find a way to these areas and start mold growth. If left untreated it will spread and will grow into the materials, requiring replacement once permanent damage is done.

A great example of some of the places where you’ll find mold is a high-humidity or high moisture environment like inside homes or buildings with water damage.

Roof leaks, flooding, damp basements, and more situations can lead to walls, floors, and under-carpet areas becoming saturated. When this happens mold can start growing. It’s especially a common problem in areas where severe flooding has happened like after a hurricane or a river flooding a nearby town.

Characteristics of mold

A close up view of a mold fungus.

Both mold and mildew are fungi. However, there are some differences in their appearance and how they’re treated. Note that both can lead to irritation and health problems, too!

Mold has some common characteristics you can use to recognize it:

  • A “fuzzy” appearance, much like mold growth on old fruit or bread (not flat like mildew)
  • It tends to grow in circular patterns as it expands across a surface
  • While it comes in different shades of colors (white, gray, light gray, and black) when found in homes it’s often a darker color or black (but not always)

What is mildew?

Image showing an example of typical bathroom mildew

One of the most common mildew examples – in a bathroom where moisture is present. Notice how it grows along crevices and doesn’t have the roundish growth pattern that mold does. It also has a flat appearance, doesn’t grow into materials (it remains on the surface) as mold does, and often has a slimy and/or greenish-black style.

As I mentioned earlier, mildew and mold are both fungi and have many similarities. There are a few things that set it apart from mold, however:

  • Growth pattern & appearance: Often looks greenish-black and slimy. Unlike “fuzzy”, taller growth of mold, it’s flat
  • As it spreads it grows in crevices (like between bathroom tiles) and outward in a style that resembles a large dark stain. (As opposed to the circular patterns of mold you may find)
  • There’s less risk of being exposed to the toxins produced by some molds
  • Much easier to clean & clear out versus mold (using cleaning products and scrubbing, vs having to replace entire walls, floor sections, carpets, and more after mold growth)

Mildew is very often found growing on items with a damp surface like paper, fabric, leather, and other common household items that may get wet. As you may already have noticed, bathrooms are some of the most common areas as there’s both moisture and organic material or residues left over it can get nutrients from.

It’s also sometimes found in higher areas such as walls or ceilings. People with basements in their homes often have the headache of fighting mildew and use dehumidifiers to help prevent it.

Why they’re potentially dangerous

It’s important to understand that both can produce spores you can inhale. However, the most dangerous exposure you’ll face is from certain kinds of molds.

Read on to find out just how risky it is!

Is mildew harmful? Is mold dangerous?

Image of a woman with headaches and a man coughing

Some of the symptoms of fungal spores are headaches, pains, respiratory problems and coughing, nausea, and much more. In extreme cases (especially when exposed to mycotoxins from black mold) permanent 

It’s not a matter of if mold and mildew can make you sick. If left unchecked, it’s a matter of when!

As I mentioned earlier, as both are fungi (plant-like organisms) they reproduce and spread by producing spores, which are tiny “seeds” carried by surfaces and air to other areas.

A closeup view of aspergillus species mold under a microscope. Mold spores are often too small to see with the naked eye and are a few microns (millionths of a meter) in size, making them microscopic and easy to breathe in.

Unfortunately, because they’re so small and able to move about, it’s very easy to inhale them.

When mold or mildew is present, it will continue to generate spores you can breathe in. This leads to a number of mild to serious health problems.

Of the thousands of molds that exist, some are known allergens (aggravating or causing skin, eye, and respiratory problems), and a few molds produce harmful mycotoxins that can cause serious problems. But all molds, in the right conditions and high enough concentrations, are capable of adversely affecting human health.Federal Emergency Management Agency (FEMA)

Symptoms and health risks

There are some common symptoms that you’ll begin to suffer from when exposed to mold & mildew:

  • Allergic reactions: Fever-type symptoms (sneezing, runny nose, red eyes, skin rash, etc)
  • Asthma attacks triggered
  • Eye, skin, nose, throat, and lung irritation
  • Excessive coughing or difficulty breathing; shortness of breath or tight chest
  • Headaches, various pains, and more

These are some of the less serious side effects of exposure. More serious and extreme consequences can include:

  • Infections of the skin or mucous membranes
  • Fatigue
  • Nervous disorders
  • Vomiting, loss of appetite, weight loss
  • Chronic bronchitis
  • Memory loss, “brain fog”, bleeding lungs, blindness, and brain damage

While less common than the first ones I listed, don’t take it for granted. In fact, I’ve had a reader message me about the second list – these symptoms have to be taken seriously!

Black mold vs mildew and others

Example of black mold growing in a home on a wall

Black mold growing in a home (where a sink was located, now removed) on a damp wall.

So-called “black mold” and “toxic black mold” are common names for one particular type of mold: the scientific name stachybotrys chartarum. It’s sometimes associated with gypsum material and wallpaper as that’s a common place for it to start growing.

Not all do, but unlike many forms of mildew & common mold, some forms of black mold can produce toxins leading to much more serious health effects. In fact reports of the possible harmful effects of black mold have been around since the 1930s.

In 1994 the US Center for Disease Control verified that in Cleveland, Ohio, a number of infants became sick and died from bleeding in the lungs after very high exposure to black mold spores.

Even famous people are black mold victims!

Image of Tom Leykis radio host

Former syndicated radio show host Tom Leykis, once the host of one of the most popular radio shows, suffered the permanent effects of black mold in his home.

To really drive home the point, here’s an excellent example of why you shouldn’t ignore black (or other) types of mold.

Once the host of one of the most popular syndicated radio shows in America, The Tom Leykis Show, Mr. Leykis suffered from harsh health problems. He now has a permanently changed voice after the effects of a black mold infection years ago in his Hollywood Hills home.

Do air purifiers help with mold?

Diagram showing how air purifiers help with mold spores

Air purifiers do in fact help with mold because they’re able to capture spores and remove them permanently from the air. However, it’s important to understand that it’s critical to get rid of the source of spores – by removing mold & mildew at their source.

Air purifiers can help with mold by removing spores permanently from the air you breathe.

They work by circulating the air in a room and permanently trap contaminants including mold spores as they pass through a high-density filter. Good quality air purifiers use a high-efficiency particulate air (HEPA) type of filter.

HEPA filters use a very dense fiber material and follow a quality standard – meaning their air cleaning efficiency is proven. By this standard, they’re capable of eliminating 99.97% of all air particles passing through them down to an incredibly small 0.3 microns in size.

(A micron is a unit of measurement and is 1 millionth of a meter in size – far smaller than your eyes can see).

They’re not the ONLY answer – it’s important to treat the source!

If your home or other building has a mold problem, it’s critical to treat the problem at its source! Continual exposure to mold spores is a health risk.

Air purifiers can help with the symptoms (in this case mold spores in the air you breathe) but they’re not the last solution. It’s very important to treat mildew and mold properly at its source.

Don’t risk your health by ignoring the problem!

If the source of the problem isn’t treated it will grow and can produce even more spores, endangering your health more and more as time goes on.

Don’t jeopardize your health! Treat mold and mildew at their source. In many cases since mold can grow into surface areas such as walls, carpets, and more in some cases these have to be replaced and repaired.

How hard is it to get rid of mold and mildew?

Example of mold on wall and cleaning products for removal

Mildew can often be treated with cleaning products, leaving surfaces unharmed. Sometimes a good scrubbing bush is needed, too. I’ve been able to clean mildew easily many times using a solution of bleach and water.

Mold, however, is a different story – especially if it has had time to grow further into surfaces. Mold removal is best left to experienced professionals as in many cases walls, floors, ceiling sections, and more will must be replaced. Mold exposure should be dealt with the right way too.

For best results, if you have moisture or high humidity you can prevent mold by ensuring leaks or water sources are completely stopped or by using a dehumidifier.

Grant Williams

About the author

Grant is a professional engineer by trade and has experience with both maintenance and do-it-yourself home projects. He enjoys sharing his expertise & ideas with others to help them improve their comfort and quality of life. Read more »

Your comments are welcome!

  1. What would happen if you were to ingest eat some of this mold by accident black mold kind of greenish. There’s mold mites around my place but a few and I have this is going to sound stupid I have mold growing on me . most of my body actually nobody can seem to figure out what’s wrong with me but I know what’s wrong with me I adjusted some of the mold it’s been for 4 months I have all the symptoms and have green I can pull back my skin and there’s the mold and I can pull it back far enough and there’s skin.. they’re not 3 months extremely bad the last 3 weeks my feet are not even normal anymore a lot of other problems and I’m still in the same damn apartment any advice help.. thank you

    • Hi, Stephen. If you believe you’ve got an extreme skin condition like that you really need to see a dermatologist to get it properly diagnosed. As far as ingesting it, I suspect most likely nothing will happen due to the stomach’s acidity. However, I’m not sure in the case of toxic black mold.

      Definitely I’d go speak with a health professional and don’t put it off any longer. Best regards.


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