What is mildew?

When you think of mildew, your first instinct is probably to think of the smell. Mildew has a distinct, musty smell, which is one of the main reasons why it is so unappealing. Another reason is that it tends to spread, giving it a sinister, insidious feel. Mildew is also connected in our minds with the idea of being unclean, so we have a visceral aversion to it.

Despite this, mildew is actually a relatively simple and benign problem to have in your home – if dealt with promptly. Unlike mold, it rarely causes health problems, and it also doesn’t penetrate below the surface it is found on. It’s relatively simple to clean, and quite straightforward to prevent.

Understanding mildew, therefore, removes much of our instinctive revulsion and, while we might not want it in our home, shows how it gets in and how we can get rid of it.

WHAT IS THE TAXONOMY OF MILDEW?

Mildew is a type of fungus. Fungi are classified as their own kingdom, separate from plants and animals. The fungi kingdom includes things like:

Yeast

Mushrooms

Molds

Unlike animals, fungi ‘eat’ by secreting enzymes that break down food. They then absorb the nutrients that result from this decomposition. By contrast, fungi are not like plants, as they do not make their own food via photosynthesis. Instead, they take nutrients from their environment. This is what causes objects to decay around them. Mildew is most commonly used to refer to plant-based diseases.

THERE ARE TWO MAIN TYPES OF MILDEW:

Powdery

Downy

Both of these refer to mildews that affect plants and agricultural products. Mildews are most commonly found in agricultural or horticultural settings, although, in the popular consciousness they are most associated with causing odor and decay in high moisture areas within the home.

What does it look like?

White, gray, or yellow. Mildew most commonly looks like a white, gray, or yellow growth on the top of an area that is both warm and moist.
Starts out light, then darkens. Unlike mold, which can be green or black, mildew remains light until it begins to grow. As the mildew spreads, it will darken in color.
Powdery or downy. Mildew also has a distinctive texture; this depends on whether it’s powdery or downy.

Mildew can look almost like dust or powder on a surface when it first appears. However, it soon spreads, meaning that the patches start appearing in multiple locations, usually separated by distances of around half an inch or less. This gives a surface a ‘blotchy’ appearance.

What is its role in the ecosystem?

Mildew’s specific biological function is to feed on cellulose and other plant materials. Mildew is most commonly found in the wild on plant leaves or on products such as potatoes.

Within the ecosystem, this aids with the decomposition of plant material, thereby ‘recycling’ plant nutrients so that they can pass up the food chain once again. Mildew requires high humidity in order to thrive.

This gives us clues as to how mildew behaves when it gets into homes. Because it feeds on cellulose, it is attracted to surfaces such as wood and paper (which includes wallpaper). It is unlikely for mildew to grow on tile, for example, as this does not provide it with nutrients. This also demonstrates why mildew can be so problematic – because it effectively ‘eats’ wood and paper, it can cause extensive damage to furniture and walls.

WHAT IS THE DIFFERENCE BETWEEN MOLD
AND MILDEW?

For more detailed information on the specific differences between mold and mildew, see our article mildew vs. mold. In summary, however, while mold and mildew are both fungi and both enter your home, infesting areas of high moisture, there are differences between the two.

FEATURE	MOLD	MILDEW
COLOR	Can be blue, green, yellow, brown, gray, or white.	White, yellow, or gray; turns brown as it ages
TEXTURE	Fuzzy or slimy	Powdery or fluffy
BLEACH TEST (place a drop of bleach on affected area)	Will remain the same color	One of two types
DAMAGE CAUSED	Mold can damage the structure it grows on	Mildew tends only to harm the ‘food’ it grows on
HEALTH PROBLEMS	Mold has been connected with several respiratory problems	Inhaling mildew spores may cause some coughing
REMOVAL	Mold removal may require professionals	Mildew removal is a job you can do yourself

WHAT ARE THE HEALTH IMPACTS
OF MILDEW?

As with mold, the most damaging aspect of mildew from a health perspective is the spores. Both mold and mildew release spores, which are microscopic particles designed to help mildew spread to new areas.

However, these spores are easy to inhale and once they get into your lungs they can cause respiratory problems – particularly for those who already suffer from some form of health problem.

Common symptoms of inhaling spores are:

Physically touching mildew (or mold) can also prompt allergic reactions – it’s best to use gloves and a mask when cleaning mildew, and keep children and animals away from any patches.

The most at-risk people from mildew are young children and the elderly, as well as groups such as pregnant women or those who are immunocompromised.

Although mildew is far less harmful than mold – if you experience a reaction to mildew, you should consult a physician and look to remove the mildew as quickly as possible.

DOES MILDEW DAMAGE
SURFACES?

The good news is that, unlike mold, mildew rests only on the surface of an object. Mold actually consumes and decays the surface it lies on.

For example, if mildew is on a piece of wooden furniture, it is likely not to have permeated the wood. Cleaning it off with a mildew cleaner and a soft cloth or brush will preserve the furniture’s integrity.

By contrast, if mold was on the same piece of wooden furniture, then it is likely that it will have permeated into the material and caused damage to the wood.

Mildew tends only to affect the ‘food’ that it actually grows on rather than the underlying surface. This can cause problems if mildew is growing on cellulose-based products, such as wallpaper or some forms of insulation.

However, unlike mold, mildew does not commonly consume household products – preferring plants, flowers, and agricultural products.

HOW CAN I
PREVENT
MILDEW?

Since mildew is carried on tiny spores, often over large distances, it’s almost impossible to prevent it from entering your home. However, what you can do is prevent the conditions that allow mildew to grow.

WHAT MILDEW NEEDS TO GROW

Mildew requires the following four conditions to survive:

Food

Air

Water

Suitable Temperatures

Temperatures between 41 and 104 degrees Fahrenheit

In order to prevent mildew, you need to remove one of the four elements. The easiest one to get rid of is moisture.

Since mildew tends to grow in areas of high humidity or where there is moisture (such as a leaking pipe) you can prevent it by simply drying the area.

Some ideas for how to dry out an area:

Sometimes removing mildew is a case of regularly opening windows to ventilate a space.
However, if you have persistent problems, then a small dehumidifier will help to dry out a room and get rid of mildew’s water supply (our page on the best dehumidifiers compares various dehumidifiers available and their features).
Fixing leaky faucets and pipes will also help to prevent mildew from taking hold.

HOW CAN I GET
RID OF MILDEW?

Once you have mildew, it can spread very quickly throughout your home. Mildew can germinate and grow in 24-48 hours. After three days, mildew releases spores, which take hold and become visible after about two weeks. Therefore, mildew can spread very quickly over a large area of your home. The trick is to treat it quickly.

Luckily, mildew is easy to remove (at least in comparison with mold). Where mold often requires professionals to come in, you can remove mildew yourself – often with household implements.

FIRST, PROTECT YOURSELF

The first thing to do is to put on a pair of rubber gloves. Since mildew spores can cause irritation, you should be as protected as possible. You can also wear a face mask and goggles if you have them available.

THEN, CLEAN

There are commercial mildew removers available from hardware stores, although you can also mix bleach and water to create your own.

To do so:

Mix one cup of bleach in a gallon of warm water
Using a bristled brush, immerse in the water and then scrub the surface
Once you’ve removed the mildew, soak the brush in the bleach solution
Be sure to thoroughly dry the area you have cleaned to prevent mildew from returning

You should also monitor the area you have cleaned, and repeat the process if necessary.

Mildew is a lot less damaging to health and home than mold. However, they flourish in the same conditions, so if you have a mildew infestation, you should address it immediately as it may lead to a more damaging mold infestation.

By keeping your home clean and dry, and cleaning surfaces as soon as you notice mildew, you can head off the problem before it gets too difficult for you to handle yourself.