What are mold and mildew?

Both mold and mildew are fungi that develop as a result of excessive, unchecked moisture in confined spaces, and both often are found in the home, especially in damp areas that have been subjected to water damage. In fact, mildew is simply a particular type of mold with a flat growth pattern.

There’s a lot of confusion about the difference between mold and mildew, likely because of how much these two organisms have in common. But some key characteristics differentiate them — and dictate how to get rid of them.


Differences between mold and mildew


Mold looks slimy or fuzzy, while mildew is powdery.

There are two primary ways to identify whether you have mold or mildew growing in your home: sight and smell.

Mildew usually looks white or gray and dry, even powdery. It always appears flat, growing outward in a pattern along small crevices (like between bathroom tiles) in a shape resembling a large, dark spill. Mold, on the other hand, often is raised and can be green, red, blue, or black. It can appear almost “fuzzy,” especially when found on food, or even slimy in nature. When mold is present on a surface, it usually appears in an irregular spotted pattern.

Another way to identify the difference is by smell. Mildew has a milder, musty smell that some compare to damp socks, but mold smells stronger and more pungent. As mold grows, it produces pungent microbial volatile organic compounds (MVOCs).


Mold burrows, but mildew grows on the surface.

Mildew and mold can be found on wood products, ceiling tiles, cardboard, wallpaper, carpets, drywall, fabric, plants, foods, insulation, decaying leaves, and other organics — all materials containing cellulose. Glass, plastic, concrete, and metal provide no food for organic growth and cannot, without some sort of biofilm present, support mold.

Most homeowners know that mold or mildew are likely to show up in damp, dark, warm areas like basements, bathroom walls, and anywhere with past water damage. And while mold growth in a home can happen due to unfortunate events like flooding, it can grow even with “normal” home conditions. Mold loves warmth, darkness, oxygen, and moisture. Mildew, in particular, thrives in humidity, which is why you’ll see often it in shower stalls and on windowsills.

Mold-welcoming environments can be found all over your home, from your shower to your mattress to the insulation in your attic. Some other common spots include:


  • In crawl spaces
  • Around showers and bathtubs
  • In ceilings, near exhaust fans or recessed lights
  • In or near areas where water is dripping (drainpipes, gutters, etc.)
  • In the wall near the clothes dryer vent
  • Near HVAC vents
  • Under carpeting


Mold’s primary purpose in nature is decomposition — for that reason, it spreads quickly and burrows, causing structural and cosmetic damage inside your home. Mold growths, or colonies, can start to grow on a damp surface as quickly as 24 to 48 hours after spores are sown. While mildew can cause damage, it’s usually more cosmetic in nature. It’s a good idea to inspect your home for both regularly.


Mildew can cause some health issues, but effects from mold are more severe.

The presence of mold and mildew in the home can have an effect on the health of humans and pets. The severity of these mold exposure symptoms can range depending on your age and overall health.

As a fungus, mold reproduces and spreads by producing spores, reproduce through tiny “seeds” carried by surfaces and air to other areas. There are health risks associated with the presence of both mold and mildew spores, but the effects of mold — especially black mold, or Stachybotrys chartarum — are much more severe.

People can suffer mild respiratory problems, sore throats, and headaches from mildew. Mold, on the other hand, can go so far as to affect the nervous system and result in memory loss, headaches, mood changes, and depression. Mold also can cause skin and eye irritation, congestion, respiratory illnesses, and general aches and pains.

Air purifiers can help with the symptoms (in this case, mold spores in the air you breathe) but they’re not a lasting solution. It’s very important to treat mildew and mold properly at its source.


Treating mold and mildew


Prevention is the best method for keeping your family healthy and your home free of damage.

Keep all surfaces dry. Your bathroom and kitchen are especially prone to dampness. Also, remember to leave your washing machine open between uses so it can air out.

Use a dehumidifier. To prevent mold and mildew from growing, keep your home at an ideal humidity level (between 40-50%).

Change your air filters regularly. HVAC and space filters can easily grow mold and mildew, as they’re designed to collect spores and other particles.

Inspect for mold and mildew regularly. The earlier you catch it, the easier it will be to treat.

Keep the air in your home circulating. Stagnant air traps humidity, which creates the perfect environment for mold and mildew to grow. Keep the flow in your home by opening windows and using fans.

Use an indoor air purifier. Indoor air purifiers can remove spores from the air in your home, helping to prevent them from forming clusters and growing.


Mildew can be removed with household products and cleaners, but removing mold is more complicated.

A major difference between mold and mildew is how to eliminate each. Standard household cleaning products and a good scrubbing brush work on mildew, which exists on surfaces. Once a fungus has been identified as mold, though, it’s important to establish what kind of mold it is. Some types of mold can be removed with bleach or specialized cleaning products while wearing protective gear, while others, namely toxic black mold, require hiring a mold removal professional. Either way, we recommend leaving identification and treatment to the pros.


Key takeaways


Mildew is a kind of mold, which means the fungi have a lot in common. They are both found inside homes, thrive in moist environments, spread from surface to surface easily, and may cause problems with your health and your home. The easiest way to differentiate them is by appearance, with mildew taking on a flat, spill-like pattern and mold tending to be more spotted and fuzzy.

Though mildew does tend to be less severe than mold, both should be treated as potential health risks. Preventive measures will go a long way in keeping your home and family healthy. Mildew is usually safe to scrub away yourself, but mold remediation requires a professional to look below the surface.