"Damp building" is a mix you breathe. Mould spores and fragments, irritant chemicals off waterlogged drywall and carpet, plus the dust mites and bacteria that bloom in the same wet places. Fungal proteins are potent allergens; the rest irritates airways even in people who aren't allergic.

Occupants of damp buildings run up to 75% higher risk of respiratory symptoms and asthma ¹. Pooled odds ratios sit around 1.3 to 1.8 across cough, wheeze, and asthma ², and the causal tie to childhood asthma flares is now formal ³.

What the evidence does not show is the "toxic mold" story. Airborne mycotoxin in even filthy buildings sits orders of magnitude below the dose that poisons animals ⁴. The real disease is pedestrian: irritated airways, allergic noses, sensitized lungs. Pedestrian, and worth fixing.

The fix is moisture control, not chemistry. The EPA, CDC, and WHO all say the same thing.

Not on the list: routine spore testing, urinary mycotoxin panels, "mould-illness" supplement stacks, ozone generators. A HEPA purifier helps during cleanup but never replaces fixing the building.

The turnaround runs in weeks.

• First week after the leak's patched and the wet drywall is out: the musty smell you'd stopped noticing lifts.
• Weeks: morning congestion shortens; night cough drops off; the daily antihistamine you assumed was for "allergies" starts getting forgotten.
• Weeks to months: remediated homes cut adult asthma outcomes by roughly 40%, with less medication and fewer symptoms ⁸.

Two limits stay honest: allergy you've already built to Aspergillus or Alternaria doesn't reverse, though reactivity eases as the spore load drops; and fatigue or brain fog you've pinned on "mould illness" has no strong evidence it clears with remediation ⁴.