Mold is a kind of fungus. Tiny spores are everywhere — outdoors, indoors, on surfaces, in the air. Most of the time, your body handles them without you noticing.
Mold becomes a concern when moisture lingers indoors and lets a colony grow on building materials. The species, the amount, and your individual sensitivity all matter.
Common indoor sources of moisture
- Plumbing leaks behind walls, under sinks, around toilets
- Roof leaks
- Bathrooms with poor ventilation
- HVAC systems that condense water and don't drain it
- Floods, even ones that "dried out" days later
When to take a closer look
If you notice any of these in your home, hotel room, or rental, it's worth investigating:
- A persistent musty or earthy smell
- Visible discoloration on drywall, ceilings, or grout that wasn't there before
- Symptoms (sinus, sleep, brain fog) that worsen in one specific building and improve when you leave it
- A history of water damage in the building
What this is not
This is general information, not a diagnosis. If you're concerned about a health condition, please talk to a qualified practitioner. If you're concerned about a property, an inspector or testing service can give you data — see the testing services page.
We meet people where they are. Many readers come to us scared and dismissed by other systems. You are not crazy for asking these questions.
Further reading
- Symptoms people commonly report
- Mold testing explained
- For the medical side, many in our community reference the Shoemaker Protocol and work with a mold-literate practitioner.