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12 Harmful Types of Mold Commonly Found in Homes

by Amanda Demsky
types of mold

How Many Different Types of Mold Are There?

New molds are discovered almost every year. Today, there are over 100,000 types of mold, but only several hundred have been thoroughly studied.


When wondering “How many different types of mold are there?,” what really matters are the types of mold that are more-likely to be in your home. The bad news is that there are over a hundred molds that thrive in homes and all of them are capable of causing harm and destruction. The good news is that, unlike outdoor molds, indoor molds can be subdued and eliminated.

Types of Mold

A common misconception is that some molds are safe (“moldy cheese”) and some molds are dangerous (“black mold”). In truth, studies have confirmed that all molds have the potential to cause harm at some level.

Three Levels of Harm Caused By Mold:

  • Allergenic: Molds that can cause allergies and allergic reactions, such as asthma attacks.
  • Pathogenic: Molds that can cause disease, especially in those already suffering from an acute illness or who have a compromised immune system.
  • Toxigenic: Molds that produce toxic substances (i.e. mycotoxins, aflatoxins, etc.) that can cause deadly health issues. Otherwise known as “toxic mold.”

Whether they’re the “milder” types of mold on bread or the more harmful types of toxic mold, all types of mold can be classified under at least one of these three levels.

12 Harmful Types of Mold Commonly Found in Homes

Acremonium first starts out as a small, moist mold but later turns into a fine, powdery substance. It is usually gray, orange, pink, or white and grows anywhere there is condensation, such as cooling coils, draining pans, humidifiers, and window sealants. It’s a good friend of strachybotrys (mentioned below) and the two are often seen growing together. That’s not the only scandal acremonium has caused. It’s an extremely dangerous pathogenic and toxigenic mold, in fact. Exposure to acremonium can lead to various cancers, impaired brain function, and disease in the bone marrow, immune system, and other vital organs. It causes many of the same symptoms as strachybotrys, which can read further down this list. (Allergenic/Pathogenic/Toxigenic)

Alternaria is the most common allergenic mold in all the world. It’s a velvety-looking mold that sports dark green or brown “hairs” (hyphae). Alternaria thrives in damp conditions. In fact, if there is water damage (new or old) in any part of the home, it’s a sure bet that alternaria has set up shop there. Alternaria’s favorite pass-time is to wreak havoc on the upper respiratory tract. It is more commonly associated with asthma or asthma-like symptoms and skin conditions around the nose and mouth. (Allergenic)

Aspergillus is probably one of the more common household molds, especially since there are over 185 species of it. Some have suggested that it’s more recurrent molds in North America, but no logical explanation as to why this could be has been submitted. It comes in an array of different colors, depending on the species, and grows in thick layers, forming long chains of mold growth along various surfaces. Aspergillus isn’t too picky about the materials it adheres to, unlike other molds. But, like other molds, it prefers warm, damp, and dark spaces, too. Some species are toxigenic and produce aflatoxins (deadly carcinogens), while most are only allergenic. As an allergenic, it’s keen on causing asthma attacks, lung infections, and respiratory inflammation. As a pathogenic and toxigenic mold, it dabbles in disease and cancer mostly of the respiratory system (but has been known to affect other vital organs). (Allergenic/Pathogenic/Toxigenic—depending on the species)

Aureobasidium is an allergenic mold worth mentioning because of how quickly and intensely the eyes, nails, and skin can develop an infection after brief physical contact. (Dermatitis, or skin rash, is probably the most common complaint for those who meet aureobasidium. Never touch it with bare skin!) It is usually pink, brown, or even black in color but, as it matures further, it will appear dark brown. Some molds can only metabolize organic materials, but aureobasidium doesn’t mind synthetics, such as certain glues, which is why it is usually found growing behind wallpaper or on painted walls. Wooden surfaces are another one of its favorite hangouts. (Allergenic)

Chaetomium is a cotton-textured mold that goes through several stages of color as it matures (from white to gray to brown and, finally, to black). Chaetomium doesn’t stand out much in terms of living preferences. It’s enjoys damp, warm conditions like any other mold, however, it is mostly found in leaky roofs, pipes, basements, and sink areas. It’s most recognizable trait is its unique musty odor, which is slightly different from other molds. Just don’t go sniffing around, trying to tell the difference. Chaetomium is not just an allergenic mold, it’s toxigenic, too, and is especially dangerous to children and those with compromised immune systems. (Allergenic/Pathogenic/Toxigenic)

Cladosporium is another gem of the allergenic crew. What makes it special is how it can thrive in both warm and cold conditions, unlike other molds that need continual warmth. It is olive-green or brown with a texture that resembles suede and can be found in carpet, fabric, upholstery, under floorboards, and inside cupboards. Like most allergenic molds, cladosporium causes the typical symptoms, such as respiratory issues and dermatitis, but it goes the extra mile and subjects its victims to skin lesions and infections of the lungs and sinuses. (Allergenic/Pathogenic)

Fusarium can be pink, red, or even white and is very similar to cladosporium in many ways, including the ability to thrive in warm and cold temperatures. Within the home, it grows in water-damaged spaces and is usually found in carpeting, wallpaper, and other fabrics. Fusarium is a sucker for food products and compost heaps, too. Unlike cladosporium, however, fusarium can become toxigenic. Exposure to fusarium can lead to not only mold illness but, if contact is continued and proper treatment is neglected, fusarium will cause severe and life-threatening conditions. Bone infections, brain abscesses, central nervous system damage, hemorrhages, and internal bleeding are just a few tricks fusarium has up its sleeve. (Allergenic/Pathogenic/Toxigenic)

Mucor can be white or gray in color. It grows rather quickly and displays itself in thick patches. Its favorites spots are near or within HVAC systems, ducts, window A/C units, and especially within materials that are thick and damp, such as unkempt carpeting. Mucor is mainly skilled in causing respiratory issues and worsening the effects of a pre-existing asthma condition. It also dabbles a little in flu-like symptoms (fever and general malaise). Prolonged exposure, however, can result in a fungal infection known as mucormycosis. Mucormycosis can damage the sinuses, lungs, and brain, as well as infect the eyes and nose. Like a Candida yeast infection, mucormycosis can also infiltrate the blood, digestive system, and renal system. Thus, it can gain access to and damage the body as a whole. (Allergenic/Pathogenic)

Penicillium is probably the most recognizable mold. It is blue or green with a velvet-like texture and can be found in food products (i.e. penicillium is more commonly known as one of the types of mold on bread), water-damaged buildings and materials, such as carpet, wallpaper, ductwork, and even mattresses. Penicillin is incredibly dangerous for those with immune disorders as it worsens their condition but, for the most part, it’s just a regular allergenic joe. When it’s not busy tormenting those with pre-existing conditions, penicillin is usually occupied with irritating the respiratory system (i.e. pulmonary inflammation and asthma) and cultivating chronic sinusitis. (Allergenic)

Stachybotrys is the wicked “black mold!” This bad boy lives in spaces saturated with moisture, prefers humid climates, and will take root in almost any material but favors those made of cellulose (i.e. cardboard, hay, paper, wicker, wood). For being the notorious slimy black mold that it is, it’s interesting to know that it’s more-often dark green in color, instead of black. Nevertheless, stachybotrys has truly earned its nefarious reputation as one of the most dangerous types of toxic mold. This is because it matures quickly, spreads rapidly, and releases millions of mycotoxins into the air that cause severe health problems. First-time exposure may only produce the following symptoms: burning sensations in airways, a tightening in the chest, cough, nose bleed, fever, and a long, painful headache. In the case of frequent exposure, this dark green—uh, black—mold will cause even further difficulty in breathing, sinusitis, and chronic fatigue. Most victims of frequent exposure to stachybotrys complain of dull, relentless aches in their joints and sinuses, in addition to the sudden onset of depression. Children are especially susceptible to it. Studies show that stachybotrys is responsible for several neurological issues in children, as well as pulmonary bleeding in infants. (Allergenic/Pathogenic/Toxigenic/Evil Villain)

Trichoderma is the name for a family of mold that is mostly white with green patches. If it is able to develop colonies, its growth will be rapid and a wool-like texture will appear on its many clusters as it further matures. Wherever there is dampness or condensation, you can trust a trichoderma family member to pay a visit. But, don’t let it stay too long, trichoderma is notoriously for causing not only mold illness but severe rot and decay in a home’s structure or whatever material it takes root in. Most trichoderma molds are non-pathogenic but there are some that are known to cause pulmonary and liver infections. Trichoderma also produce mycotoxins, which makes it a rather potent foe. (Allergenic/Pathogenic/Toxigenic)

Ulocladium is a lover of water. “Dampness” and “humidity” just won’t cut it for ulocladium. This black-colored mold is insistent upon wet environments and is typically found in buildings that have been flooded. Kitchens, bathrooms, basements, and even windows prone to heavy condensation are among its favorite hideouts. It doesn’t like to live alone, either. Oftentimes, stachybotrys, fusarium, and chaetomium keep it company within the same space. Because of its coloring and preferences in habitat, ucloadium is often confused for several different molds, which is why an expert may have to come and help identify it. An expert should probably be called anyway, since ulocladium is dangerous to those with allergies, immune disorders, and capable of causing hay fever, skin infections, asthma-like symptoms, and general difficult in breathing. (Allergenic/Pathogenic)

Mold Symptoms

There are those more vulnerable to mold. Some may have mold sensitivities due to an overactive immune system or they are experiencing other conditions that are already taxing their immune system. According to research, children, pregnant women, people with pre-existing health conditions, and seniors are more susceptible to toxic mold exposure. For people who have weaker constitutions, an allergenic mold may affect them as intensely as a pathogenic mold may affect a healthy, robust individual.


Symptoms may vary by person but, too often, the initial signs of fungal exposure are mistaken for the common cold or flu. Most medical professionals are not trained to identify mold illnesses and know very little about addressing the root of the problem. Instead, they may prescribe medication that only masks the symptoms or further damages the body’s natural ability to heal itself. Therefore, it is important to know how to identify mold and mold symptoms, and to eliminate it quickly from both body and home.

Mold Symptoms Due to “Mold Sensitivity,” First-Time Exposure, or Exposure to Allergenic Mold

  • Chest and nasal congestion
  • Coughing, sneezing, and wheezing
  • Shortness of breath
  • Asthma
  • Sore throat
  • Watering, dry or sore eyes
  • Skin irritation
  • Headaches

Some people are more sensitive to molds to begin with. Others develop a severe sensitivity over time. If given enough time, continual exposure to allergenic mold spores could result in an overactive immune system (mold sensitivity). This means that symptoms that could have easily been mistaken for the common cold will eventually mimic the symptoms associated with the more toxic molds because other systems of the body will be overwhelmed by the immune system’s overachiever efforts and not function optimally. In addition, with increased exposure comes the increased risk of mold spores actually taking root and colonizing within the body. Once this happens, some allergenic mold would be capable of becoming pathogenic.

Pre-Existing Conditions Most Vulnerable to Mold Exposure

Individuals with compromised immune systems and any pre-exisiting conditions should be even more careful of protecting themselves from mold. Healthier individuals may experience mold sickness and allergy-like reactions to mold, but those in poor health will face infection and, quite possibly, death.

  • Allergies
  • Asthma
  • Chronic Obstructive Pulmonary Disorder (COPD)
  • Chronic lung disease
  • Cystic fibrosis
  • Depression
  • Diabetes
  • Heart defects
  • Liver failure
  • Kidney failure
  • Sickle Cell Disease
  • Seizure disorders
  • And much more…

Severe and Chronic Conditions Caused by Pathogenic and Toxigenic Mold Exposure

  • Cancer
  • Digestive and heart conditions
  • Immune and blood disorders
  • Impared brain function
  • Liver and kidney conditions
  • Neurotoxicity (toxic nervous system)
  • Pregnancy conditions
  • Pulmonary bleeding
  • Pulmonary fibrosis (scarring in the lungs)


Mold is such a critical problem that the Institute of Medicine (IOM), World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), and even the Bible all warn strongly against its dangerous effects. Depending on the type of mold, the length of exposure to it, and the original health of those exposed, a mold’s toxicity can have a long-lasting—and even deadly—effect on human health.

Now that we’ve taken a look at just how harmful even the “mildest” of molds (like moldy cheese) can be and have an idea of how to identify various types of mold and mold symptoms, please feel free to share your thoughts and experiences below in the comments section. What molds have your found in your home? Have you experienced any of the symptoms mentioned above? What words of advice can you give other readers who may be experiencing and learning about mold for the first time?


About the Author: Amanda Demsky is the mother and personal chef of two boys, the domestic technician of a three-bedroom desert home, and occasionally, a freelance writer and editor. Feel free to follow her on Twitter fullquiver777.

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Kevin Wiley May 17, 2018 - 9:45 am

This is useful information that can be used to determine the types of mold and the circumstances being exposed to them. Definitely an eye opener. I actually came across your site from a link found on http://www.molderadicator.com and I was impressed on the amount of knowledge provided on the subject.

thewife May 23, 2018 - 9:16 am

Kevin, thank you for your comment. We appreciate your input. I just made a quick visit to http://www.molderadicator.com/. What a helpful and informative site! It’s great to see we’re not alone in the fight against mold!

Kristin Lamb December 16, 2018 - 7:11 pm

My apartment was flooded by the upstairs neighbors water heater about five months ago . There have been multiple instances in my building they have six other apartments with flooding issues the landlord only comes in and wipe things up with a towel and put a dehumidifier. Now I have found thick black mold with the white like hair is all underneath my bathroom sink all inside of a closet . Me and my daughter have been severely sick she’s had fever as high as 103.1 your infections upper respiratory infections I have had strep throat major headaches depression . My landlord just wants to clean it with bleach I don’t know who to call about the situation I can’t afford to stay in a hotel who do I contact to help me ?

Frank February 11, 2020 - 7:44 am

Thank you for the excellent article. We perform mold removal in homes (http://www.truproremediation.com) but dealing with health effects of mold is a completely different thing.

Rebecca Gardner November 24, 2020 - 12:33 pm

I appreciate how you mentioned that Fusarium mold is pink or red and commonly found due to home water damage. I noticed a patch of something red-colored when I cleaned my bathroom floor for the first time in a while this morning. Maybe I’ll look for a water damage contractor to check out my home and make sure there’s not another issue I’m unaware of!


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