Black mold vs. mycotoxins: what's the difference?

Black mold and mycotoxins, explained

Why some molds are black

Mold color mostly comes from pigments in the spores and cell walls. Many dark molds produce melanin, the same family of pigment found in human skin, which helps protect them from ultraviolet light and drying out. It’s a survival trait shared by a lot of species. It says nothing about whether a mold makes mycotoxins. Color also changes with age, moisture and the material a mold is growing on, so the same species can look quite different from one wall to the next.

Common dark molds indoors

Mold	Typical appearance	Where it’s often found	Mycotoxin notes
Stachybotrys chartarum	Dark green to black, slimy when wet	Drywall paper, ceiling tile, soaked cardboard	Some strains make macrocyclic trichothecenes. Others make atranones instead.
Cladosporium	Olive green to black	Window frames, bathrooms, outdoor air	Not generally considered a major mycotoxin producer
Alternaria	Dark gray to black	Window frames, showers, outdoor air	Makes some mycotoxins, studied mainly in food
Aspergillus niger	Black, powdery	Damp surfaces, food	Some strains can make ochratoxin A
Aureobasidium pullulans	Cream or pink, darkening to black	Caulk, grout, painted surfaces	Not usually associated with mycotoxins

Molds that aren’t black but can make mycotoxins

• Aspergillus versicolor, often green or yellowish, is common on damp building materials and makes sterigmatocystin.
• Penicillium species, often blue-green, include some that make ochratoxin A or citrinin.
• Chaetomium starts white to gray and darkens with age. It grows on long-wet drywall and wood and makes chaetoglobosins.
• Aspergillus fumigatus, usually blue-green to gray, is associated with gliotoxin.
• Fusarium, often white to pink, can make trichothecenes on very wet materials.

If you’ve found pale mold and wondered whether it matters, is white mold dangerous? covers it in more detail.

How Stachybotrys became black mold

Stachybotrys chartarum got its reputation in the 1990s, when a cluster of infant illnesses in Cleveland was linked to it in an early investigation. The CDC later reviewed that work and concluded the association had not been proven. By then, toxic black mold had become a common phrase in news stories and lawsuits. The science behind it is more careful: Stachybotrys can make potent toxins, not every strain does, and plenty of other molds make toxins as well. The organism itself is covered on our page about what Stachybotrys is, and its toxins on trichothecenes and Stachybotrys.

None of this means Stachybotrys should be taken lightly. When it’s confirmed, it usually signals a long-running water problem and a sizable amount of damaged material, and both deserve a careful, contained cleanup. The point is that the same care belongs on every mold problem, whatever it looks like.

What matters more than color

• How long materials were wet. Weeks of wetting on cellulose favors Stachybotrys and Chaetomium. Brief dampness favors faster molds.
• How much is growing. A small patch on a window sill is a different job from a whole wall cavity.
• Where the dust has gone. Toxins travel on dust, so the rest of the house and the HVAC system matter.
• What the lab says. Identification and a mycotoxin panel answer the questions color can’t.

Whatever the color, the removal principles are the same: fix the water, contain the area, remove what can’t be cleaned, capture the dust and confirm the result. If you’re dealing with confirmed Stachybotrys, our black mold removal page describes that project.

We identify and remove mold and mycotoxins in buildings. We don’t diagnose or treat medical conditions, and nothing on this page is medical advice. If you’re worried about exposure, please talk with a doctor. With your permission, we’ll share our test results with them.