4 Types of Mold to Avoid at All Costs

warning to avoidMany people are surprised to learn that mold has many faces. Rather than being a single thing called ‘mold,’ there are numerous species and sub-species to consider. The visible appearances are different, the microscopic appearances are distinct, and there are varying levels of toxicity.

What this means, basically, is that some types of mold are far more dangerous than others. Virtually every type of mold is problematic in some way, but the most toxic kinds of mold are especially dangerous. Even a moderate exposure can lead to all manner of complications throughout the human body.

So what are the ugliest, most dangerous varieties of mold? Is it possible to important to find and eliminate them before they bring ill-effects to your family, guests and employees?

The definition of toxic mold

When you hear someone mention ‘toxic mold,’ they’re referring to any type of mold with the ability to generate mycotoxins. What are mycotoxins? Scientists still aren’t sure exactly why mold produces them. What’s certain is that mycotoxins are a danger to humans and animals. They can lead to acute conditions throughout the body, especially the respiratory system and the brain.

Aspergillus and Penicillium

This is the most frequently occurring toxic mold in residential and business environments However, there are many sub-species of Penicillium and Aspergillus. Although all of them are harmful to your health, only certain ones are positively toxic.

This variety of mold is often mis-identified due to its highly variable appearance, and its resemblance to other species of mold. Lab testing is all the more important in this case. Prevention is relatively simple, since this type of toxic mold is almost always found in unusually damp, dank indoor spaces.


Fusarium is another mold with a long list of sub-species. The toxic varieties are very bad news in terms of human or animal health. Problems involving the eyes frequently occur, and fungus can also take over fingernails and toenails. If your immune system is weaker than normal for any reason, Fusarium infections tend to grab hold faster and become much worse. Most often, you’ll see Fusarium in a brown or red color.


When you think of a mold that’s truly ugly and dangerous, Stachybotrys comes to mind. This toxic mold has an appearance like black slime and is highly toxic. You may have heard mention of ‘black mold’—that would be Stachybotrys. There is a very long and disturbing list of health complications that can arise from prolonged exposure to this mold. Avoid and prevent at all costs.


If see a fuzzy white mold that looks almost like cotton, the last thing you want to do is ignore it. You could be dealing with Chaetomium, another toxic mold. The appearance of this mold will sometimes grow darker as the colony grows.

Fortunately, this one isn’t known for causing extreme reactions in people (although it can happen). Most often it causes allergies to flare up and results in moderate infections. However, if a person’s immune system is compromised in some way, it’s possible to get a “deep infection” from Chaetomium. The complications of such an infection can be extremely severe.

The Importance of Lab Testing

As you can see, it’s very difficult to tell exactly what kind of mold you’re dealing with—and how toxic it may or may not be—without a proper lab test. The good news is that mold testing is widely available, safe, and relatively cost-effective—especially when you consider the far greater costs of allowing one of the toxic molds listed above to set up shop in your home or business.

We hope you’ve found this information helpful, and we welcome your questions or comments below!