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Comparison of mold and mildew growth patterns

Mold vs Mildew: What's the Difference?

Both are fungi, but they differ in appearance, health risks, and how you should handle them. Here's what you need to know.

The Quick Answer

Mildew is a surface fungus that is usually flat, powdery, and gray or white. It grows on damp surfaces and is relatively easy to clean with household products.

Mold penetrates deeper into materials, appears fuzzy or slimy, and comes in various colors (black, green, blue). It's harder to remove and poses greater health risks.

Key Differences at a Glance

Mildew

  • Flat, powdery texture
  • White, gray, or yellowish color
  • Grows on surface only
  • Common on shower walls, windowsills
  • Usually easy to clean
  • Mild musty smell

Mold

  • Fuzzy, slimy, or raised texture
  • Black, green, blue, or other colors
  • Penetrates into materials
  • Grows anywhere with moisture
  • Often requires removal of materials
  • Strong musty or earthy odor

How to Identify Each

Identifying Mildew

Mildew typically appears as flat patches that are easy to wipe away. You'll commonly find it:

  • On bathroom tiles and grout
  • On windowsills with condensation
  • On damp fabrics and paper
  • On leather goods in humid closets

If it wipes away easily but returns quickly, treat it as a moisture problem and address the source. Visual identification is imperfect, so when in doubt, treat it as mold.

Identifying Mold

Mold is harder to identify because it grows in many forms and colors. Look for:

  • Fuzzy or velvety patches
  • Colors beyond white/gray (black, green, blue, orange)
  • Growth that returns after cleaning
  • Visible damage to the material beneath
  • Strong musty odors even without visible growth

If you're unsure, treat it as mold. Learn more about common indoor mold types and their characteristics.

Health Risks

Mildew Health Effects

Mildew can cause mild respiratory irritation, especially for people with allergies or asthma. Symptoms are typically:

  • Coughing and sneezing
  • Mild throat irritation
  • Headaches in poorly ventilated areas

Mold Health Effects

Mold exposure can cause a range of symptoms. Severity depends on exposure level and individual sensitivity. Common effects include:

  • Respiratory problems and wheezing
  • Allergic reactions (runny nose, red eyes)
  • Asthma attacks in sensitive individuals
  • Skin irritation and rashes
  • More severe reactions in immunocompromised people

Learn more about mold health effects and when to see a doctor.

Treatment Approaches

Treating Mildew

Mildew is usually a DIY job. Effective approaches include:

  • White vinegar (spray, wait 1 hour, wipe)
  • Hydrogen peroxide (3% solution)
  • Commercial mildew cleaners
  • Baking soda paste for stubborn spots

After cleaning, address the moisture source: improve ventilation, use a bathroom fan, or run a dehumidifier.

Treating Mold

Mold treatment depends on the extent of growth:

  • Small areas: Clean with mold-specific products, wearing N95 mask and gloves
  • Porous materials: Often need to be removed (drywall, carpet, insulation)
  • Large areas: Hire a certified remediation professional
  • Always fix the moisture source first

See our guide on when cleaning works vs. when materials need removal.

When to Worry

Mildew: Usually Not a Major Concern

Mildew is annoying but rarely dangerous. Worry if:

  • It keeps coming back despite cleaning and ventilation
  • You notice it spreading to new areas
  • You develop persistent respiratory symptoms

Mold: Take It Seriously If...

  • The affected area is larger than 10 square feet
  • You see mold in multiple rooms or areas
  • Mold has penetrated walls, floors, or ceilings
  • There has been water damage or flooding
  • You smell mold but cannot see it (hidden mold)
  • Anyone in the home has health symptoms
  • You have recurring mold despite cleaning and drying

Color alone is not a reliable indicator of risk. Learn about black mold facts vs. fiction and finding hidden mold.

Next Steps

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Action steps for mildew and mold

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