Difference Between Mold and Mildew
Mildew is a surface fungus that is flat, powdery, white or gray, and grows on damp surfaces. Mold grows in and under surfaces, appears fuzzy or slimy, comes in various colors, and can cause structural damage. Mildew is easier to clean; mold often requires more aggressive treatment.
Key Takeaways
- Mildew is technically a type of mold but is commonly distinguished as a surface-level fungus.
- Black mold (Stachybotrys) is particularly concerning and often requires professional removal.
- Both mold and mildew can trigger allergies and respiratory issues in sensitive individuals.
Explanation
Mildew is technically a type of mold but is commonly distinguished as a surface-level fungus. It appears powdery or fluffy, usually white, gray, or light yellow, and grows on damp organic materials like paper, fabric, leather, and bathroom surfaces.
Mold is a broader category of fungi that grows deeper into materials. It can appear in many colors - black, green, red, blue - and has a fuzzy, slimy, or even hairy texture. Mold penetrates porous surfaces and can cause structural damage to buildings.
Mildew is generally easier to remove with household cleaners and scrubbing. Mold, especially on porous surfaces, may require specialized products, professional remediation, or removal of affected materials. Both indicate excess moisture that should be addressed.
Both mold and mildew thrive when relative humidity exceeds 60% and temperatures fall between 77-86°F (25-30°C). Keeping indoor humidity below 50% using dehumidifiers or ventilation is the most effective prevention. Bathroom exhaust fans should run for at least 20 minutes after showering, and any water leaks need to be fixed within 24-48 hours—mold can begin colonizing a damp surface in as little as 24 hours.
Testing kits available at hardware stores for $10-50 can identify the specific type of mold present. The most common indoor molds are Cladosporium (olive-green or brown, found on fabrics and wood), Penicillium (blue-green, found on water-damaged materials), and Aspergillus (varies in color, common on dust and food). Stachybotrys chartarum, often called "black mold," produces mycotoxins and requires professional removal when the affected area exceeds 10 square feet, according to EPA guidelines.
Things to Know
- Black mold (Stachybotrys) is particularly concerning and often requires professional removal.
- Both mold and mildew can trigger allergies and respiratory issues in sensitive individuals. Using rubbing alcohol can help disinfect small mildew patches.
- Mildew on houseplants (powdery mildew) is a different fungus from bathroom mildew.
- Painting over mold without treating it first allows the mold to continue growing beneath the paint layer and eventually push through.