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What’s the Difference Between Mold and Mildew?

Do you smell a musty odor coming from your washing machine or your basement? Do you see spots of green muck growing underneath a sink or on the grout of your shower tiles? Wondering if those unpleasant odors or icky spots are mold or mildew? If so, you aren’t alone. So many homeowners are perplexed when it comes to mold and mildew; mainly, they wonder if there’s a difference between the two, or if there is actually any difference between the two at all.

While the words “mold” and “mildew” are commonly used interchangeably, the truth is that there are differences – albeit, slight – between the two. Understanding those differences is important, as it will allow you to be better identify and treat these substances. To learn more about the nuances between mold and mildew, including how to identify them, the potential impact they can have on your health, and how to treat and prevent them from growing in your home, keep on reading. With the information presented below, you’ll be well-armed in the battle against mold and mildew, and will be able to effectively protect your home, your family, and yourself.

Is there a difference between mold and mildew?

Mildew is a type of mold, so in essence, these two substances have a lot of commonalities. For example, both are fungi that occur naturally, thrive in locations where moisture is present, and spread via spores that they release, travel through the air, and land on surfaces. While in nature, both mold and mildew can actually be beneficial, but when they grow inside, they can cause issues, both for your health and for your home.

Given the fact that mold and mildew share so many commonalities, you’re probably wondering, “Well, aren’t the two really the same thing?” While yes, some characteristics are the same, there are also some elements that differentiate mold and mildew. Let’s explore further so that you can see for yourself those differences, including the appearance and scent of each type of fungi, where they grow, and the potential risks that are associated with them.

What is mold?

Since mildew is a type of mold, it’s first important to understand what mold is.

As mentioned, mold is a type of fungus. Actually, according to Wikipedia, “Molds are a large and taxonomically diverse number of fungal species…”Like other types of fungi, such as mushrooms and yeast, mold is a naturally-occurring substance that grows on organic matter, such as plants, fallen leaves, wood, fibrous materials (linens and other types of materials), food, and any other kind of object that is organic in nature. Believe it or not, molds actually serve a purpose, as they aid in the decomposition of dead organic matter. As mold consumes whatever it grows on, it releases the nutrients that those items contain back into the soil so that other types of living organisms can use them. In other words, it functions as a natural recycler.

Though it’s beneficial and actually necessary in natural, when it grows indoors, mold can be a serious hazard. In addition to the risk of health issues that exposure to mold growth can cause, mold can also cosmetically and structurally damage the surfaces that they grow on indoors, such as walls, floors, fabrics, carpets, etc. Mold spores are all around use. They’re airborne and microscopic, so they are constantly floating through the air and they are invisible to the naked eye. When those airborne spores land on surfaces, if the conditions are right, they’ll reproduce and develop into clusters, and it’s these clusters that they become visible and can be identified.

Molds thrive in moist, warm (anything above freezing) environments, and as mentioned, they feed on organic matter. Therefore, mold growth can occur in any area where the temperatures are above freezing, and where moisture and organic matter is present.

How does mold growth occur indoors?

As discussed, mold spores are all around us. Those spores can easily float indoors through open doors and open windows, cracks in walls, roofing, and foundations, and they can even collect on shoes, clothing, hair, and anything else that you bring outside and then back inside. When those spores get inside, they float around and eventually land on surfaces. As long as moisture is present and the temperatures are above freezing, those spores can grow into clusters. Once those clusters grow, more spores will be released, and the cycle continues. As such, it’s easy to see why indoor mold growth can become a serious problem, as it grows and spreads rapidly.

Where does indoor mold growth occur?

As mentioned numerous times, indoors, mold growth can occur anywhere moisture, warm, and organic material is present. In other words, there are so many locations where indoor mold growth can occur. With that said, some of the most common locations where indoor mold growth is found include:

  • Poorly ventilated areas
  • In humid areas
  • In bathrooms, kitchens, laundry rooms, basements, and attics
  • Around plumbing pipes
  • In cabinets
  • Under sinks and appliances that use water or produce moisture, such as washing machines, fridges, and dishwashers
  • Along windowsills
  • In and around air conditioning units and HVAC systems
  • On fibrous materials, such as walls, carpets, wood flooring, grout, insulation, linens, and furniture

As you can see, mold can grow pretty much anywhere in your home.

The effects of indoor mold growth

When it grows indoors, mold growth can become seriously problematic. Firstly, it can damage the structural integrity of whatever it grows on. For instance, if it’s growing on walls or floors, it will eat through the surfaces, and will eventually degrade them to the point that they can become structurally unsound and could even crumble. Of course, this can put you and your family in danger. For example, if you’re walking on a mold-infested floor that has become weakened enough, you could potentially fall right through the floor and suffer a serious injury.

Mold isn’t only dangerous to structural and decorative elements; it can also be damaging to your health (apart from possibly becoming injured by mold-damaged structural elements). Mold, as discussed, produces airborne spores, which means that they can be inhaled. Mold spores have been identified as allergens, and as such, breathing in those spores can cause adverse reactions in individuals who suffer from allergies. Mold exposure can be damaging to individuals who do not otherwise suffer from allergies, too. Examples of some of the adverse health effects that can be caused by mold exposure include:

  • Nasal congestion
  • Sneezing
  • Chest tightness
  • Coughing
  • Irritated eyes and throat
  • Wheezing
  • Shortness of breath
  • Confusion
  • Irritability
  • Listlessness
  • Malaise

In serious situations, it can even lead to the development of respiratory health conditions.

Individuals who suffer from allergies or who have been diagnosed with a preexisting respiratory health issue, such as asthma, chronic obstructive pulmonary disease (COPD), or emphysema, for example, are more prone to developing complications as a result of mold exposure; however, anyone can experience adverse effects when they are exposed to mold over a prolonged period of time. Additionally, children and older adults are more susceptible to mold-related health issues. 

There are several different types of mold, but some of the most common varieties that are linked to adverse health effects include:

  • Alternaria
  • Aspergillus
  • Caldosporium
  • Penicillium
  • Stachybotrys

Identifying mold

Because mold spores are airborne and are all around us, as long as the conditions are right, they spores can accumulate and quickly grow and spread throughout your house, which can cause structural and cosmetic damage, as well as the above-mentioned health issues. As such, in order to combat the problems that are associated with mold, being able to identify it is a must so that you can take the steps that are needed to eradicate it.

There are two primary ways to identify mold:

  • Sight. You can notice mold growth by sight. When it begins to multiply and grow into clusters, mold can grow into what appears to be fuzzy patches that can vary in color, including green, brown, black, white, yellow, gray, and even blue, and pink. If you see any splotches that seem to have these characteristics, it’s likely mold growth.
  • Smell. While mold doesn’t always produce a strong odor, it can, and when it does, the scent can be musty. When mold grows, it releases gases that are known as microbial volatile organic compounds (MVOCs). It’s not only the mold that you’re smelling, but it’s also the chemical compounds that are released during different stages of mold growth. If you smell a musty-like odor, there’s a very good chance that mold is to blame.


What is mildew?

As indicated, mild is a type of mildew. Like mold, it can grow wherever moisture is present, but the primary difference between mold and mildew is where it grows; mold can grow on virtually any surface, but mildew tends to grow primarily on flat surfaces.

In a home, the damage that mildew does is usually cosmetic; however, in nature, mildew can be quite destructive, particularly to plants and crops. Additionally, like mold, mildew can cause health issues, but the health-related effects usually aren’t as severe as the issues that mold can cause.

As per the US Federal Emergency Management Agency (FEMA), mildew is early-stage mold. It’s less harmful than mold, and it’s easier to eradicate it.

How does mildew impact health?

When it grows outdoors, mildew is largely known for the damage it can cause to plants and food crops; however, it can also negatively impact physical health. The negative impact occurs for the same reason that mold-related health issues happen: inhalation of the spores that the fungi produces. Mildew can cause the same health issues that mold can cause, and many of the symptoms are similar, including:

  • Nasal congestion
  • Eye irritation
  • Throat irritation
  • Headaches
  • Coughing
  • Wheezing
  • Skin irritation

Like mold, if mildew is not treated, it will continue to reproduce and release more spores, and as such, the health effects that are associated with exposure will worsen. If you or a family member suffers from allergies and are experiencing any of the aforementioned health issues, checking for mildew growth is highly recommended.

Where does mildew growth occur?

Typically, mildew grows on flat surfaces. Common examples include on windows and window sills, walls, showers, and floors; basically, on flat surfaces where moisture is present and where the temperature is above freezing and a food source is present.

How to detect mildew

Just like any other type of mold, mildew grows and spreads fast. The damage mildew growth causes usually isn’t as bad as the damage caused by mold growth. Usually, the damage is cosmetic and it can be removed without a lot of hassle. Like mold, there are two primary ways that mildew can be identified, including:

  • Sight. Mildew tends to have a powdery texture. When it first grows, the color tends to be white, but in time, it can become yellow, brown, or black. All kinds of mildew are flat in appearance.
  • Smell. Like other types of mold, mildew tends to create a musty odor, and that odor is caused by MVOCs. If you notice a musty odor in your home, the source could be mildew or other types of molds. When you detect this scent, a visual inspection will confirm whether you have mold or mildew growth.


Can you prevent and eliminate mold and mildew growth in your home?

Now that you know the similarities and differences between mold and mildew and are aware of how to identify them, you are probably wondering if there are ways that you can prevent and eliminate it. As the saying goes, “the best defense is a good offense”; in other words, when it comes to mold and mildew growth, preventing it from growing in the first place should always be your first approach.

Mold and mildew prevention

In order to prevent mold and mildew growth in your home, here are some tips that you can use:

  • Keep things dry. The less moisture in your home, the better, as mold and mildew thrive in damp environments. Wipe down any surfaces that get wet, such as countertops, floors, and shower walls. Keep the lid of your washing machine opened, and prop open the door of your dishwasher so that they can air out.
  • Ensure your home is properly ventilated. When possible, keep windows opened, and when it not possible, make sure that you run exhaust fans. Always run exhaust fans or keep windows open when you’re taking showers.
  • Make use of a dehumidifier; ideally, the relative humidity level in your home should be between 40 and 50 percent.
  • Change out air filters on a frequent basis, including HVAC and HEPA filters, as they are prone to accumulations of dirt and debris, and mold and mildew can grow on the surfaces and be recycled back into your home.
  • Get in the habit of inspecting your home for mold and mildew on a regular basis. Check surfaces and pay attention to musty-like odors.


Hire a Reputable Mold Inspection and Testing Company

Often, mold and mildew growth can go undetected. You may smell musty odors, but you may not be able to see the fungi growth. To ensure the safety of your home and your family, hiring a reputable professional that specializes in mold inspection and testing is highly recommended. MI&T, one of the most trusted mold testing companies in the country, uses the most advanced equipment and state-of-the-art strategies to detect mold and mildew growth on surfaces and within the air of your home.