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Black Mold vs Mildew: What’s The Difference?

Black Mold vs Mildew: What’s The Difference?

An unfortunate fact of homeownership that most people won’t tell you about is that no matter how clean and spotless your home is, eventually you’re gonna get fungal growth, a nasty off-color stain that just keeps getting bigger. Especially in hot and wet climates, every nook and cranny is a goldmine for any kind of organism looking to grow and multiply. 

These microorganisms come in all shapes and sizes, but after years of working with home renovators, I can tell you that in most cases, you’re either dealing with mold or mildew. However, these two are like night and day and it’s crucial for the integrity of your home and yours and your family’s health that you’re quick to identify which is which. 

Why? You ask. Well because one of them can cause major structural damage to your home, as well as produce serious health complications or even death, while the other will just be unsightly at best and at worst will cause some headaches and flu-like symptoms. So read on and I’ll tell you what you can do to keep your loved ones safe and prevent costly mold remediation.

Mold & Mildew: What Are They?

While both mold and mildew are the results of fungal growth caused by high humidity in your home, they couldn’t be more different, so let’s talk about what sets them apart. 


Mildew is by far the most benign of this pair, it usually shows up on plants, crops, and even food that has gone bad. While it can wreak havoc on crops and large scale agriculture, it’s no cause for concern to find some mold growing on your plants. Thankfully, it only grows on surfaces and it does so at a flat rate. That means that it will not increase exponentially as it expands. 

You’ll encounter mildew in two different ways, as a white, powdery substance or as a lesion or discoloration, these are called powdery and downy mildew respectively and in both cases will grow in patterns on top of whatever they’ve infected. 

Much like mold, it can produce adverse health effects when inhaled, but these are often milder, such as allergy or flu-like symptoms. However, you should still address mildew as soon as possible since the issues may get worse over time. 

1. Powdery Mildew:

The most common form of mildew out there, it is actually caused by many species of fungi of the Erysiphales order. You’re most likely to encounter it in agricultural products that need to be grown in greenhouses, thanks to the high humidity and temperature.

Farmers of such crops need to be diligent about eradicating it via biological or chemical methods since it can drastically decrease crop yield. 

2. Downy Mildew:

This one is a lot harder to spot since it only shows up as a slight discoloration or lesion on leaves, turning them yellowish and eventually brown. It favors cooler conditions and is most common for vegetables that grow on vines and crucifers such as cabbage, broccoli, and cauliflower. Unlike powdery mildew, this one is only a minor threat to agricultural endeavors and is usually handled by generic pesticides.


The term mold actually refers to thousands of species of fungi that present similar behaviors. Like being multiplying astonishingly fast if the right conditions are given, the plethora of health effects they can cause, and the fact that they not only grow on surfaces but actually penetrate whatever it’s infected. It may not seem like a big deal at first but it can lead to MILLIONS in property damage. 

Not only that, but mold is also a lot more harmful to humans if inhaled than mildew can ever be, depending on what kind of mold has appeared in your household, you might be subject from anything ranging from headaches to vomiting to death. With that in mind, here are the most common types of mold out there:

  • Acremonium – It can take months or even years for these spores to build up enough to be visible, at which point they’ll appear as a white, powdery substance. It can lead to infections and allergies when inhaled or entering the body through small injuries.
  • Alternaria – One of the most common forms of mold, it takes on a greenish hue and a velvet-like appearance. In most cases, it is not very harmful, but can still cause headaches, nausea and allergy symptoms to those exposed
  • Aspergillus – It’s one of the hardest molds to identify because different strains take on different colors and appearances. This insidious pest can get in your sinuses and cause a bloody discharge, fever, and headaches.
  • Chaetomium – Manifesting as a brown substance that resembles cotton, this type of mold produces mycotoxins, which can lead to fevers, headaches, and more severe health effects. 
  • Mucor – An extremely toxic kind that is very prone to growing inside air ducts, this type of mold has to be dealt with quickly and efficiently to avoid major health concerns. 
  • Fusarium – It often takes on a pink or reddish appearance, this one needs a high concentration of moisture to grow, so it’s most likely to appear on damaged or leaking systems. Inhalation can lead to abscesses, lung infections and skin lesions. 
  • Stachybotrys – Often known as “black mold” for its color, this is one of the most infamous and toxic strains of mold out there. It is extremely toxic to humans, so if spotted, professional help is a must. 

Where Does Mold & Mildew Grow in A House?

As we’ve mentioned previously, both mold and mildew thrive in hot, humid conditions. Unfortunately, most homes have plenty of spaces that fit that criterion. You can find mold and mildew anywhere from damp patches on ceilings and bathrooms, window sills, shower walls, even air ducts. This is especially true for homes that have been water damaged, be it by flooding, leaks, or heavy rains. It can even lead to the growth of the toxic black mold we described above. 

To learn more about preventing mold and reducing humidity, check out our article about plants that absorb humidity.

Signs You Have a Mold or Mildew Infestation

1. You can see it. 

Of course, the most obvious sign you have an infestation in your home is actually seeing the mold or mildew in plain sight. However, both mold and mildew star out as microscopic particles, meaning that by the time they are visible by the naked eye, your home might already be overrun and your health already affected. 

2. You begin developing symptoms. 

As mentioned earlier, before the spores become visible by the naked eye, they might already be floating inside your home. As you inhale them you might begin developing mild symptoms such as headaches, allergies, nausea, or irritation of your eyes. If the symptoms are sporadic and quick to disappear when you leave your home, you might be dealing with a mold or mildew infestation. 

In any case, always be sure to consult a medical professional if you see your health deteriorate. 

3. You notice weird smells. 

Even before you develop symptoms, these fungi can already be multiplying inside your home. As these organisms digest matter and reproduce, they release gasses as a byproduct, which will have a distinct musty smell which is hard to miss. 

What Do I Do If I Have a Mold or Mildew Infestation?

Determine Whether It Is Mold vs Mildew

Mildew is a low easier to get rid of than mold, so if you find yourself staring at weird stains on your walls, furniture or appliances, it’s understandable that you might want to know what you’re dealing with. 

Lucky for you, there is a simple test that can reveal the nature of your infestation. Just apply a few drops of bleach and leave it for a couple of minutes. If it fades – its mildew. If it doesn’t – its mold. In any case, if you’re in doubt it’s always safer to call professionals for help and testing. 

If it’s mildew:

Count yourself lucky, because mildew can be treated with common household cleaning products. Since it only grows on surfaces, simply getting rid of the spores might be enough to eradicate the infestation. Clean it using bleach and try to keep the area ventilated and free of moisture from here on out. 

If it’s mold.

In this case, there is very little you can do to clean the mold yourself. As I stated above, it penetrates the infected surfaces, meaning that you won’t be able to get rid of it with surface cleaning. Even worse, it can survive extremely harsh environments, so even abrasive chemicals might not be enough. 

The responsible thing to do here is to call professional mold removal companies that can deal with the problem and ensure that your home is safe for you and your family to live in. Here at RestorationUSA, we pride ourselves in locating and working with the best companies to provide you with the assistance needed. 

For more on mold, visit the Mayo Clinic website.