How to Tell the Difference Between Black Mold and Mildew

How to Tell the Difference Between Black Mold and Mildew

Did you know that mold forms 24 to 48 hours after water damage? Mold and mildew grow in places difficult to detect and spread quickly. An infestation of harmful fungi could even drive you out of our home. 

But which kinds are dangerous, and how are you supposed to know? This guide will explain the difference between black mold vs. mildew and what to do about them. 

Black Mold

Homeowners often use the terms mold and mildew interchangeably, but they are not the same. The differences are crucial to know when it comes to identifying black mold vs. mildew. The characteristics of black mold, common types being Aspergillus cladosporium and Stachybotrys atra, are as follows.

Black mold is a slimy greenish-black growth that accumulates in moist or damp areas, especially those with a high cellulose concentration, behind sheetrock and wood framework. The first signs of infestation are usually the musty, dank odor (like rotting vegetation), as the growth often starts between the walls or under the flooring. 

Mold spores can be knocked loose with a simple breeze and spread to new areas in the home. These spores attach to surfaces, and this is how mold forms. And it doesn’t take long for the spores to spread: around one to three days. 

Symptoms of Black Mold Exposure

Mold can cause symptoms in people with allergies or those exposed for a prolonged period. Frequent symptoms of mold exposure include:

  • Scratchy throat
  • Coughing
  • Dry, scaly skin 
  • Sneezing 
  • Postnasal drip
  • Nasal congestion
  • Itchy eyes or nose
  • Asthma attack 
  • Wheezing 
  • Chest tightness 


The term mildew refers to various molds or fungi with a flat appearance and foul, earthy smell. It is generally less damaging than black mold as it doesn’t move through surfaces and the effects on homes are typically cosmetic. Mildew ranges in color from white to yellow to dark brown or black. 

Black Mold Vs. Mildew: What’s the Difference?

Black mold typically forms on damp surfaces or near a water source like trim along bathroom walls and porous, carpeted, or wooden surfaces. The patches are circular, form patterns, and may feature fuzzy white or green patches. 

Mildew may appear on a damp surface as a white, grey, or light yellow powdery substance. Over time it may darken and spread in an irregular pattern. If you don’t know what you’re dealing with, black mold or mildew, call in a specialist. 

Remediation specialists can explain all of the benefits of mold inspection, including telling you what type of growth you’re dealing with and getting rid of the problem. 

Eliminate Mold and Mildew Now 

Regardless of whether you’re dealing with black mold vs. mildew, both have potential health consequences. Having the issue handled by a mold remediation professional is the best way to go. In the meantime, reduce moisture by using a dehumidifier and moisture barriers. 

If you found this guide helpful, then take a look at the rest of our posts for more articles like this! 

Paul Petersen