What Kind of Mold is Dangerous?

Mold can be a scary thing.

Especially if you find out that you’re living with it.

But, the truth is that not all molds are created equal.

And although more than 100,000 species have been identified, only some molds can be quite dangerous to your health while others may just give you a sneeze.

So, “What kind of mold is dangerous?”

That’s the question we’ll answer for you in this guide.

By the end, you’ll know exactly which types of mold can cause the most harm to you and your family.

What Mold is Dangerous?

Before we get into what mold is dangerous, let’s first look at mold in general.

This fungus can be found everywhere on the planet, even in Antarctica.

Thus, if you’re trying to find an environment where you can escape mold, there isn’t one.

However, not all molds are harmful to your health.

In fact, you may have mold growing right next to you or floating in the air around you and it’s not causing any kind of problem.

Therefore, some molds are dangerous and others are not, which we’ll go over next.

Different Types of Mold

In general, mold species are separated into three categories:

  • Allergenic
  • Pathogenic
  • Toxigenic

Allergenic molds are those that are unlikely to make you ill, although they may aggravate mild allergies.

Pathogenic molds can cause infections in individuals who are immunocompromised.

Toxigenic molds are the ones that are dangerous to animals and humans who come into contact with them.

What Kind of Mold is Dangerous? Toxigenic Mold

Toxigenic molds are definitely the fungus species you want to worry about.

People often refer to them as “toxic mold”, and they can certainly cause health issues, but it’s not the mold itself that’s toxic.

It’s actually the mycotoxins (a chemical metabolic byproduct) that toxigenic molds produce which are the harmful substance.

Mold spores, on the other hand, are how molds reproduce.

The spores are so tiny that they can’t be seen by the human eye and travel on air currents until they find a suitable place to settle.

In your home, mold spores often cling to ceilings and walls, but it can be anywhere, including furniture, clothing, carpets, and other surfaces.

If moisture, the right temperature, and a food source are present, the mold spores will begin to grow.

Mycotoxins are not used during mold reproduction, but they may travel with the spores. They have also been found traveling on dust or tiny pieces of wallpaper.

Since both spores and mycotoxins are so small and travel in much the same way, there’s an increased risk of inhaling them.

This is when they become a problem for your health.

However, it’s important to remember that just because there might be a toxigenic mold species present, that doesn’t mean they’re producing mycotoxins.

The mycotoxins must be present for the mold to be harmful to your health.

Toxigenic Molds

Some of the most common toxigenic molds that are found inside the home include:

  • Fusarium species
  • Penicillium species
  • Aspergillus species
  • Stachybotrys chartarum

Within each of these categories (except the last one, which is its own species), there are many different species that have various harmful qualities.

The symptoms created by these species can range from an allergic reaction to a deadly illness.

In many cases, these species will grow in places you wouldn’t suspect, including in the basement, inside walls, or under carpet.

We’ll now look at each species more in-depth.


Many Fursarium species can be found growing on water-damaged carpets and fabrics, including furniture.

It’s often orange in color, and exposure to the mycotoxins created by the various species can cause mild allergic reactions, asthma, or more severe respiratory infections.

It has also been found that Fusarium is linked to certain gastrointestinal illnesses issues with women’s reproductive systems.


There are approximately 200 known species when it comes to Penicillium, and they’re incredibly common in the air and soil.

It’s often found on foods and other perishable goods, but they can also grow in damp areas in your home such as walls, floors, and carpets.

Penicillium mold comes in various colors, including blue, yellow, green and white. It is most known for causing asthma problems and infections in the kidneys, lungs, and liver.


There are also more than 200 species within the Aspergillus family, but only 16 of them are known to cause illness—and none of them are fatal if you get them treated.

This mold is yellow-green and is often found indoors in carpeting.

Despite the fact that this mold is the least harmful of those on the list, you still need to get it taken care of if you find it growing in your home.

Letting Aspergillus grow could lead to respiratory infections and a condition called hypersensitivity pneumonitis, which is caused by inflammation in the lungs.

Stachybotrys chartarum (Black Mold)

When it comes to wondering what mold is dangerous, this is the species that most people think about.

It’s most commonly referred to as “black mold” and its spores will produce harmful mycotoxins if they’re disturbed.

Stachybotrys chartarum can be found growing on substances that have high amounts of cellulose, including wood, ceiling tiles, gypsum board, and other organic materials.

Problems that might arise when exposed to this toxigenic mold species include:

  • Aches and pains
  • Respiratory issues
  • Problems with your central nervous system
  • Nasal and sinus congestion
  • Chronic fatigue
  • Eye irritation
  • Cough
  • Sore throat

How to Prevent Mold Growth

Now that you know what kind of mold is dangerous, you might also be wondering how you can prevent mold from growing in your home.

The best way to reduce mold growth, especially when it comes to toxigenic molds, is to make the environment unpleasant for them.

Mold needs four things to thrive:

  • Moisture
  • Warmth
  • Food source
  • Low light

That’s why you often find mold growing in kitchens, bathrooms, basements, and attics because those areas contain the perfect breeding ground for mold reproduction.

Reducing the amount of moisture and humidity in your home can deny mold some of the most important elements they need to survive.

It’s advised to have your pipes and air conditioner checked on a regular basis to ensure that they aren’t leaking.

If you have high humidity in your basement or crawl space, adding a dehumidifier can help reduce mold growth.

Keeping the temperature in your home below 70 degrees Fahrenheit also prevents mold from growing. It must have warmth to reproduce.

Another product you can use to stop the spread of mold is an air purifier.

Air purifiers can help strip the mold spores out of the air that causes mold to reproduce.

You can check out our best air purifier for mold and viruses guide to find out more about these helpful devices.

Air purifiers that are best for mold will need to have three types of air filtering technologies, which the linked guide above explains.

If you ever experience water damage in your home, whether from flooding or leaking pipes, it’s imperative that you have this problem taken care of by a professional.

Otherwise, the risk of dangerous mold can be exponential inside your home.

Summary of What Kind of Mold is Dangerous

As you learned, mold is a common and abundant species on this planet and there are thousands of different types that exist.

However, the answer to the question, “What kind of mold is dangerous?” is the species that fall under the toxigenic category.

Therefore, not all types of mold you come into contact with will pose a threat to your health.

In addition to learning what mold is dangerous, there are simple ways to keep toxigenic molds from growing in your home.

And most of the preventative measures work to deny mold the ability to grow.