What is the difference between mold spores and mycotoxins?

Spores, in plain terms

A spore is how a mold spreads, a little like a seed. Most are only a few microns across, far too small to see individually. Outdoor air carries them all the time, so every house has some. A spore that lands on a damp surface with something to feed on can start a new colony. One that lands somewhere dry may sit dormant for a long time.

Spores can be counted, identified and cultured. They can also be killed. A dead spore can’t grow, but it’s still a particle, and it still carries whatever was on or in it.

Indoor spore results are usually compared with an outdoor sample taken at the same time. When indoor counts run higher than outside, or the mix of molds is different, it suggests something is growing inside the house.

Mycotoxins, in plain terms

Mycotoxins are molecules. Molds make them as by-products, and not every mold makes them. Whether a given colony produces toxins depends on the species, the strain, what it’s growing on and how wet it is. The toxins end up inside and on spores, on the fine fragments of mold that break off as growth dries, and on the surrounding material and dust.

Because they aren’t alive, mycotoxins can’t be killed, don’t reproduce and don’t need moisture to persist. They’re stable, which is why they can outlast the mold that made them. Many mycotoxins have been identified, most of them through food and agricultural research. Home testing panels focus on a smaller set tied to indoor molds, such as trichothecenes, ochratoxin A, gliotoxin and aflatoxins.

Side by side

	Mold spores	Mycotoxins
What it is	Living reproductive cell	Chemical compound
Can it grow?	Yes, with moisture and food	No
Can it be killed?	Yes	No. It has to be removed or broken down.
Found in	Air, dust, surfaces	Spores, mold fragments, dust, porous materials
Usually measured by	Air spore traps, tape lifts, dust DNA tests	Mycotoxin panel on settled dust or surfaces
Normal in homes?	Yes, at some level	No accepted normal level for house dust

Why the difference matters for testing

An air sample tells you about spores in the air during the few minutes it ran. It says little about toxins sitting in the dust on a bookshelf or inside an air handler. A home can have spore counts that look unremarkable and still have mycotoxins built up from past growth. That’s why spore count results are best read as one piece of the picture.

The reverse is also true: high spore counts show mold activity, but they don’t tell you which toxins, if any, are present. A mycotoxin panel on settled dust answers that question directly, and dust DNA testing links the toxins back to the molds likely producing them.

Why it matters for cleanup

Most mold products are designed to kill spores and growth. That’s a reasonable goal for living mold, but it leaves the toxins in place. Effective cleanup removes the particles themselves, spores and fragments included, then treats what remains and tests to confirm. How those particles move through a house is covered in whether mycotoxins are airborne.

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