Types of Household Mold & Health Effects of Mold in Homes

Mold is a fungus containing small organisms that naturally break down biological materials. Mold travels as tiny spores that are light enough to float through the air, meaning that they can be found almost everywhere in our environment. When these spores rest on a damp area like a bathroom wall, they start growing and digesting the material that they’ve landed on.

Mold is becoming a common problem in most homes, and that’s why you need to know more about various types of household mold and their health effects.

A lot of people think that mold only occurs in older homes, but nothing could be further from the truth. Mold spores can develop even in a brand new home since their source is not age-dependent but moisture-dependent.

Mold comes in different forms, and while some are simply a nuisance, others can be quite harmful to human health, especially if left untreated. In this post, we’ll discuss everything you need to know about mold, including the common types, how to spot them, how to control them, their health effects, and so on.

Sources of Mold in Homes

We’ve already determined that mold spores are everywhere. In fact, there’s probably some type of mold inside your home right now. Mold spores generally enter a home through windows, vents, doorways, and cracks in the walls. They also stick to pets and people who end up bringing them home. They, however, need moisture, oxygen, the right temperature (60 to 80 degrees), and organic materials to be able to grow into visible colonies. Given that organic material and oxygen are ubiquitous elements in any home, the remaining viable cause of mold growth is generally moisture.

Moisture may enter your home as a result of flooding, excessive rain, leaks in the roof or walls, or broken pipes. Also, most modern homes are constructed in a very air-tight manner. This may be great for insulation, but it reduces your building’s ability to breathe, which in turn reduces the potential drying effects of natural air circulation. Regardless of the source, once there’s water or moisture in your home, mold will be drawn to it and begin feeding on organic materials in the home.

For this reason, mold thrives in moist areas of the home like in bathroom showers, kitchens, basements, laundry rooms, and crawl spaces. But, it can also hide in the drywall, appliances, carpet, wallpaper, furniture, floors, insulation, and HVAC systems. Moisture has the ability to grow mold in as little as 1-2 days.

Mold on roof
Mold on roof

Types of Mold

According to research, there are over 100,000 mold species. They all have different characteristics, growth patterns, and health effects. They also come in varying colors, including black, white, yellow, green, orange, brown, and pink. Some of these molds are more dangerous than others. The harmful types of mold can be grouped into the following classifications:

  • Hazard Class A: Includes molds that produce mycotoxins, which are poisonous chemicals that are highly hazardous to human health.
  • Hazard Class B: These molds cause allergic reactions to individuals within their vicinity.
  • Hazard Class C: Includes molds that mostly cause economic damage. They can also cause health problems to those with a weak immune system, the elderly, and children. 

With all this information in mind, let’s take a look at some of the common molds you may be facing:


This is a toxigenic mold, meaning that it produces mycotoxins. Exposure to acremonium can impair brain function and even cause serious health problems like damage to the immune system, bone marrow, and other organs. This type of mold changes in appearance over time. It begins as a small, moist mold and later changes to a powdery substance that can be grey, orange, pink, or white in color. Acremonium has a foul smell, making its presence hard to miss. It mostly grows in home systems, including cooling coils, window sealants, and humidifiers. It’s also known to grow alongside black mold and other stains.


This is the most common type of allergenic mold. It goes without saying the exposure causes allergies and asthma-like symptoms like watery eyes, coughing, and so on. They can also cause infections in people with a compromised immune system. Alternaria molds have a velvety texture and their hairs are dark green or dark brown in color. Like other molds, they can be found in moist and damp areas like showers, bathtubs, below leaking sinks, and other water-damaged areas. It spreads pretty fast, meaning you have to act fast before it causes significant effects.


Aspergillus is an allergenic mold, but it also has toxic capabilities depending on the environment and species around it. Inhaling these mold spores can cause Aspergillosis, which can be very dangerous to anyone with a weak immune system, a history of tuberculosis, or preexisting lung or respiratory conditions. It has long flask-shaped spores that form walls or thick layers of mold. Aspergillus grows in areas with high oxygen content. It’s mostly found in areas with rotting wood, soil, or piles of leaves. There are over 185 species of this mold and they appear in varying colors, especially in green, brown, and yellow.


This is an allergenic mold, and it’s mostly found growing on wooden or painted surfaces, and behind wallpaper. Aureobasidium is normally brown, black, or pink in color, but it turns to dark brown as it ages. It’s capable of causing eye, nail, and skin infections. Due to its ability to cause dermatitis, avoid touching it with bare skin.


This mold species are also allergenic. Its spores have been linked to allergic reactions and autoimmune diseases. You should also avoid touching it with bare hands as that can cause skin and nail infections. Chaetomium mold flourishes where there’s water damage under carpets, on drywall, wallpapers, and baseboards. It has a white or grey color that turns to black over time, and the texture is similar to cotton. It fills your home with a musty smell.


There are over 30 species of this allergenic mold. It typically causes allergic reactions. Cladosporium mold can grow in warm, as well as cold conditions. It’s commonly found in indoor materials like carpets, fabrics, mattresses, and upholstery, particularly where there’s moisture. It can also be present in the bathroom, in HVAC systems, and on the back of the toilet. This mold has a suede-like texture and is generally brown or olive green in color.


Fusarium mold has both allergenic and toxigenic properties. Exposure can cause symptoms of allergic reactions. Prolonged exposure can lead to serious health problems like damage to the nervous system, bone infection, internal hemorrhage, and mental impairment. It can spread pretty quickly, which means you have to be thorough when examining your home so as to mitigate its effects. It usually grows in areas with water damage. It’s also found on wallpaper, carpeting, and other materials and fabrics. Fusarium mold is pink, reddish, or white in color.


This allergenic mold is usually white or grayish in color and grows in thick patches. Symptoms of exposure are asthma and/or flu-like. But, it can also worsen asthma conditions and cause mucormycosis in severe cases. Mucormycosis is a fungal infection that can infect and damage your brain, eyes, lungs, nose, and sinuses. It’s mostly located near high condensation areas like HVAC systems, ductwork, and on old, damp carpets.


There’s a wide variety of penicillium mold species. This allergenic mold is greenish or bluish in color and has a velvety texture. Its main purpose is to cause perishable goods to spoil. Even though it has medicinal use, which is to make antibiotic penicillin, exposure can still cause allergic reactions. In fact, prolonged exposure can lead to chronic sinus infections and lung inflammation. It’s mostly found inside water-damaged furniture, insulation, carpeting, rotting fabrics, and so on. It’s known to spread quickly and easily throughout the building.

Stachybotrys (Black Mold)

This is a toxigenic mold that also causes allergic reactions. Symptoms of exposure include persistent cough, headaches, fever, nose bleeds, etc. Prolonged exposure has been linked to life-threatening conditions like damage to the liver and kidney. It’s particularly dangerous to kids and people with a weak immune system and preexisting respiratory issues. It’s one of the most notorious types of black mold you can find in your home. Stachybotrys has a slimy texture, and it’s black or dark greenish in color. It often grows where there are high levels of humidity on cellulose materials like wood, wicker, cardboard, hay, or paper.


This allergenic mold thrives in damp, moist areas. Most Trichoderma mold subspecies are non-pathogenic, meaning it’s not particularly harmful to humans. Even so, there are others that still produce mycotoxins. It also contains a lethal enzyme that can destroy building materials such as wood, fabric, paper products, and textiles. The longer it’s left untreated, the more costs you’ll incur to repair or restore your property. Trichoderma is white in color and has green patches. It’s mostly found on damp surfaces of wallpaper, carpet, and other similar surfaces.


Ulocladium mold thrives in areas with the highest moisture and large amounts of water. In that case, watch out for it if your property has recently suffered from water damage either from floods, a burst pipe, gradual leaks, or sewage backup. Ulocladium is also found in wet areas of the house, including bathrooms, kitchens, and basements. This type of mold is linked to severe allergic reactions and prolonged exposure causes asthma-like symptoms like difficulty in breathing. It’s black in appearance with white patches.

Effects of Mold

Although mold has a place in the ecosystem, we should strive to keep our homes from becoming their breeding ground. Mold can have a negative effect on your home. Depending on the species and the extent of exposure, it can also have lasting effects on human health.

Mold Affects the Structure of Your Home

Mold can drastically alter your home’s appearance. It often leaves spotting and marks on ceilings, walls, floors, rafters, and so on. Other than making your house unsightly, mold also has unpleasant odors. On top of these mild effects, did you know that mold can also cause serious structural damage?

Since mold feeds on organic materials, it can literally eat away house materials like wooden studs in walls, drywall, ceiling tiles, carpets, wallpaper, floorboards, and so on. This will cause such materials to rot and begin to fall apart. If left untreated for too long, mold can cause walls to fall down, ceilings to collapse, floorboards to cave in, and other serious structural damages.

Lastly, if mold is allowed to grow, it can also impair the functioning of many processes, including electrical circuits and HVAC systems.

Health Effects of Mold Exposure

As mold grows, they emit chemical compounds into the air that can pose health risks such as:

1. Respiratory allergies and asthma

Although some people can develop sensitivity with overwhelming exposure to mold, others are naturally sensitive to it. Symptoms will include things like:

  • Skin irritation
  • Sore throat
  • Headaches
  • Chest and nasal congestion
  • Coughs
  • Sneezing and wheezing
  • A runny nose
  • Fatigue
  • Watery, dry, or sore eyes, etc.

2. Infections

People with a weak immune system or pre-existing lung conditions are more susceptible to lung infections when exposed to mold. They also seem to have an increased risk of common fungal infections like allergic bronchopulmonary, aspergillosis, athlete’s foot, and thrush. Note that these infections are not only as a result of exposure to mold.

3. Respiratory conditions

Exposure to mold has also been linked to potentially causing respiratory conditions like asthma in otherwise healthy individuals. This is a huge concern, especially for healthy children who may end up developing a respiratory illness as a result of mold exposure. For those who already suffer from these respiratory issues, exposure to mold can intensify symptoms and attacks.

4. Severe and Chronic Conditions

Some mold species produce toxic substances known as mycotoxins. This is a very toxic by-product, and it can be absorbed through the airways, intestinal lining, and the skin. Prolonged exposure to these toxic substances can lead to very severe, and even fatal, conditions. Some of the most severe reactions to prolonged mold exposure include:

  • Neurotoxicity
  • Pulmonary fibrosis
  • Liver and kidney conditions
  • Difficulty breathing
  • Pulmonary bleeding
  • Digestive and heart conditions
  • Immune and blood disorders
  • Pregnancy conditions
  • Cancer

That being said, other reasons why you should investigate, clean, and remove mold from your property include:

  • Legal Issues: If you are responsible for keeping tenants safe and healthy, you’re at risk of being sued should they get sick from mold exposure.
  • Affect business: Mold growth can affect productivity in a work environment. A business with mold problems will incur huge costs in liabilities or even see a fall in its market share. Such issues mostly affect food processing plants like bakeries. For instance, mold can grow on the bread even before it leaves for the market. Needleless to say, this can affect your sales and even cause you to lose customers.

Mold Removal

Mold growth, whether in homes, businesses, or schools, should basically be eliminated and prevented for the sake of structural strength, home efficiency, and human health. It also helps to avoid unnecessary costs and improve the overall quality of life. To do that successfully, you need to learn about the proper ways to get rid of mold and its associated stains without compromising your safety or health.

a) Identifying the Mold

There are several ways of identifying mold. For starters, if you notice a musty, pungent smell, there are high chances mold could be hiding somewhere nearby. Alternatively, you can use a D-I-Y mold testing kit. There’s a wide variety of kits to choose from. Some even come with an optimal mail-in lab analysis to help you identify the type of mold. You can also spot the most visible type of mold, which is mildew.

To test for mold vs. mildew, simply put a few drops of household bleach on the infested area. If after a few minutes it lightens, then its mildew. But if it remains black, you have mold in your home. That being said, the safest and most efficient way to identify mold is to contact a professional mold inspector to do the mold testing.

Once you’ve discovered the presence of mold in your building, the next logical step is to remove it. You can do this yourself or hire a professional.

b) Fixing the Problem Yourself

You can tackle the infestation yourself if there are small amounts of mold. This can be done using commercial mold and mildew removers. Alternatively, you can use household products like vinegar, borax or hydrogen peroxide. Simply pour the liquid in a spray bottle and spray it on the surface of the mold. Then, wait for about 10 minutes and scrub the surface with a sponge. Lastly, wipe away and dry the surface with a towel.

Since you’re using water to clean, strive to speed up the drying process by ventilating the area or running a dehumidifier. Remember to wear gloves to protect your hands from the mold and cleaning detergents. A facial mask is also necessary to prevent you from inhaling the mold spores or the fumes given off by the cleaning products. Another thing to remember is to turn off the AC and furnace. You don’t want mold spores spreading all over the house. Once the mold is removed, it’s important to seal up the infested area(s) to prevent the mold from traveling to other parts.

c) Professional Mold Removal

Mold removal is such a complex undertaking. It’s not only difficult to identify, but also dangerous to handle. The removal process is more than just scrubbing infested surfaces; there are specific steps that need to be taken to ensure the mold is completely removed. In that case, it’s always best to leave the removal to professionals, especially in largely infested areas or if the mold has considerably grown. Professionals will identify the type(s) of mold in your house so as to determine the best cleaning techniques. They can also identify mold in hidden places like under flooring or inside walls.

So, what should you expect from mold removal professionals? They’ll first seal off the work area to prevent mold spores from dispersing throughout the home. This can be done using plastic sheets or tape. Then, they use mold remediation equipment like HEPA air scrubbers, commercial-strength dehumidifiers, or air movers. These types of equipment are specifically designed to completely remove the mold from its source. If there are any mold or mold stains remaining, they’ll use an antimicrobial chemical to clean it off.

Once that is done, mold removal professionals will use a sealer or an encapsulant. This helps to control the odor and keeps the treated area more resistant to water damage and mold. If your home has suffered significant damage, consider getting a professional to restore it back to its original state to ensure that everyone is safe.

Mold Prevention Tips

Mold is part of nature, so it’s impossible to get rid of it forever. Since it can’t grow without moisture, your first line of defense is to reduce moisture in your home. Indoor humidity should be kept below 60%. So, get a hygrometer to help you measure relative humidity. To reduce moisture in the air, use an air condition or a dehumidifier. Other controlling tips include:

  • Maintain a warm house during cool weather
  • Dry out wet areas in the house within 24 hours
  • Fix any problems causing dampness. This can be anything from fixing leaking pipes and ensuring there are no cracks on windows and doorways, to fixing seepage and patching up any vents, among other things.
  • Regularly clean and dry wooden floors, carpeting, walls, and the house at large.
  • Add insulation to cold surfaces to reduce condensation. This includes exterior walls, windows, and floors.
  • Keep the rooms well-ventilated to increase air circulation. This will carry heat to cold surfaces. To increase air circulation in damp areas such as the bathroom, you can open doors and windows or use a bathroom exhaust fan.
  • Another good device to use is an air purifier. Most of them have HEPA filters that are capable of trapping up to 99.97% of very tiny air particles like mold spores, thereby purifying the air from molds.
  • Finally, inspect for mold and mildew regularly. The earlier you catch it, the easier it will be to treat.

Final Words

That was quite long, but it’s important for us at Sprucebathroom.com to educate our esteemed clients on every issue affecting the bathroom space. Fortunately for your bathroom, you can mitigate mold growth by simply installing an effective bathroom exhaust fan. If you have any questions about molds and how you can prevent them from invading your bathroom and other spaces prone to moisture, feel free to drop a comment below or reach us through the “contact us” page.

Smith Edwards

Smith Edwards is a licensed plumber and writer with over a decade of hands-on construction and home improvement experience and has been providing home improvement advice for over 12 years.

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