When you find mold growing in your home, there’s no two ways about it – it’s gross. But how dangerous is it, really? The truth is that mold spores exist everywhere in nature and we are all constantly breathing them in. However, when the level of mold indoors exceeds the level of mold outdoors, that can trigger allergic symptoms in sensitive people. And the dreaded toxic or “black” mold can do some serious damage.

Here’s what you need to know about the most common types of mold, including when to call the mold remediation specialist.

Toxic vs. Non-toxic Molds

The most dangerous molds are those that release poisonous substances, called mycotoxins, that can cause death in people and animals. When we talk about the black mold that is really risky to human health, we’re referring to a type called Stachybotrys chartarum.

Some varieties of mold are black in color yet do not produce mycotoxins, so they are considered non-toxic. (Many additional non-toxic molds come in a rainbow of hues.) Non-toxic molds can cause allergic reactions or trigger asthma but don’t kill as a result of a particular poison.

However, each general category of mold can represent hundreds of different mold species, some that produce mycotoxins and some that don’t. It is impossible to tell by looking what type of mold you’re dealing with, so if you’re wondering when to call for professional mold remediation, the answer is almost always.

There are some notable exceptions to this rule – stick with us to the end for more on those.

First, we will be looking at several categories of mold and describing their appearance and reported health effects. The strains are categorized as less dangerous and more dangerous based on the likelihood of coming across a particularly deadly strain of it.

Less Dangerous Molds

The following types of mold can cause troublesome symptoms but are generally not thought to be deadly. Still, the extent of the reaction to non-toxic mold exposure is quite individual and can be severe in people who are prone to allergies.


The category of Cladosporium includes about 40 different species. It’s quite common and can be found in colors including green, gray, brown, or black. Typical locations are wallpapers, painted walls, carpets, wood furnishings, and any organic surface that is often damp.

Most Cladosporium mold does not produce mycotoxins, but has been linked to pulmonary edema and emphysema in certain people.


This type of mold grows even at very cold temps and is usually found on wet carpeting and fabric. Fusarium is most often an orangey color.

Though non-toxic, prolonged exposure to Fusarium has been linked to gastrointestinal distress and female reproductive issues. Those with asthma may be triggered by Fusarium and it can cause minor allergic symptoms as well.


The Aspergillus mold family includes almost 200 distinct species, but only 16 of them have been found to cause any kind of reaction in humans. If treated, none of those reactions is fatal. Aspergillus is often yellowish or greenish in color and pretty commonly found inside.

Beyond mild allergic reactions, the main health risk associated with prolonged exposure to Aspergillus is a respiratory infection that can lead to inflammation in the lungs if left untreated.

More Dangerous Molds

These molds need to be treated more cautiously. They each produce chemicals that are classified as poisons. Infants, the elderly, and people with compromised immune systems are especially vulnerable to toxic mold. A long but non-exhaustive list of symptoms associated with exposure includes:

  • Compromised breathing
  • Congestion of the sinus and nasal passageways
  • Sore throat and cough
  • Itchy eyes
  • Generalized aches and pains
  • Chronic fatigue
  • Nervous system issues
  • Memory loss

If problems with breathing or nervous system function become severe enough, they can lead to death.

Stachybotrys, the Toxic Black Mold

This type of mold causes serious health complications and may even induce death. It is typically found on materials that contain cellulose, an insoluble substance that makes up plant cell walls and vegetable fibers like cotton.

Cellulose is used in all sorts of manufactured products, including cardboard, drywall, and ceiling tiles. It is also found naturally in wood and can therefore affect your furniture, paneling, and home accessories.


This category has at least 200 known species and comes in a range of colors including blue, yellow, green, and white. The green Penicillium notatum is the source of the antibiotic penicillin, but many other varieties cause dangerous infections of the kidneys, liver, and lungs. Other types have been linked to asthma and interestingly, nail fungus.

Penicillium is also the type of mold found on food that has spoiled, and we all know what happens when it is eaten! This mold can cling to any damp surface, not just food, so walls, floors, and carpets are all fair game.


Chaetomium is known to produce several types of mycotoxin, but studies are limited on how they affect humans. Mouse studies have found this mold to damage the liver, spleen, and kidneys. Livestock have also died after eating feed tainted with Chaetomium.

This type of mold starts out white and cottony in texture, but as it develops it turns to gray and finally olive green in color. It is more often found inside than outside, and like other types of mold, is attracted to moist surfaces that contain cellulose.

The Last Word

Getting rid of mold in the home is clearly something to take seriously, but remember that most ill effects occur as a result of prolonged exposure. When you catch mold growth early, especially if it occurs on a non-porous surface like the bathtub, you can most likely clean it up yourself without worry.

Since you can’t know what type of mold you’re dealing with just by looking, it is wise to cover your nose and mouth and wear rubber gloves while cleaning. Better safe than sorry!

Always call a mold remediation specialist if the colony is large or occurs on a porous surface like drywall or flooring. The experts can let you know what type of mold you’re dealing with and assess whether the affected areas need to be replaced rather than cleaned. And don’t forget to call in a water removal specialist when there are signs of water damage or water issue, to prevent mold from developing in your home.