Toxic Mold Types

by Kimberley Jace on July 22, 2008

Thousands of types of mold exist, and we are exposed to many types every day. Some are dangerous only when ingested, while others give off substances that can damage health when they are inhaled. All species of toxic mold can cause allergic reactions in sensitive individuals, but only a few varieties can cause potentially deadly health problems. Fungi capable of producing mycotoxins are called toxic mold.

Mycotoxins are dangerous to everyone, even those without mold allergies. When the invisible spores of toxic mold are inhaled, the mycotoxins can begin to affect the lungs and nervous system.

The Deadliest Molds

In order of danger, the toxic molds are:

Stachybotrys chartarum

Stachybotrys chartarumStachybotrys mold looks greenish-black and grows on moist material containing cellulose, such as wood, wallpaper, and the paper covering of drywall. It does not grow on concrete. Most people become exposed to Stachybotrys by inhaling its spores, but it also can cause serious problems through skin contact. Symptoms of mold poisoning with Stachybotrys include respiratory problems, flu-like symptoms, headache, nausea, fever, nose bleeds, and skin rashes. Stachybotrys mycotoxins are thought to be extremely potent carcinogens and can suppress the immune system.


AspergillusThe Aspergillus family of molds — more than 160 varieties — are found mostly in decomposing or rotting organic material. Aspergillus infections often require hospitalization and long-term medical treatment.

  • Aspergillus fumigatus can thrive in relatively high temperatures, it often infects compost materials. It can cause an allergic reaction in those who handle decomposing materials.
  • Aspergillus niger can invade the body by being inhaled, where it can cause a “fungal ball” to grow in the lungs.
  • Aspergillus flavus can produce an aflatoxin — a deadly mold byproduct — in foods that is a potent carcinogen when ingested. Aspergillus flavus that grows on peanuts can produce an aflatoxin linked to cancer in human beings. Aspergillus flavus that grows on animal feed can produce an aflatoxin that can instantly kill animals that eat the contaminated feed.


CladosporiumCladosporium mold is generally dark green on top and black underneath, with a velvet texture. Cladosporium grows on plants, food, soil, painted surfaces, and cloth, and can even grow on fiberglass. Physical contact with Cladosporium can cause skin and nail infections. Breathing in Cladosporium spores can cause lung disease and lead to emphysema after long exposure.


FusariumFusarium usually lives in soil but is also often found in humidifiers and air conditioning systems, as well as water damaged building materials. Touching Fusarium can lead to skin and eye infections. Absorbing Fusarium spores through the skin or through breathing can lead to a hemorrhagic syndrome that causes excessive internal bleeding. Fusarium can produce mycotoxins called tricothecenes that can cause acute intestinal flu-like symptoms and can attack the female reproductive organs.


PenicilliumPenicillium grows on decaying organic material but can also live on painted surfaces and fiberglass duct lining. One form of Penicillium mold has been distilled into a useful antibiotic; but many people are allergic to the mold. In sensitive individuals, Penicillium can cause an acne-like skin condition as well as kidney infections, intestinal infections, and endocarditis (infection of the lining of the heart). People with weak immune systems, such as those undergoing chemotherapy or infected with HIV, are most likely to suffer serious side effects from Penicillium exposure.

Other molds that produce dangerous mycotoxins include Acremonium, Alternaria, and Chaetomium. But molds can have different appearances depending on the surface and conditions where they grow. The only way to know if you have a dangerous mold type is to have it tested.

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