September 28, 2021

12 Different Types of Mold Found in Houses

February 27, 2022
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Mold fungus spores are all around us every day, in the air we breathe and even in the wind that blows into our interior spaces. In the natural world, these spores play an important part in breaking down natural matter; however, when they get inside homes and form colonies, they not only look unsightly but also pose health risks.

Most people want to know, “what type of mold is dangerous in a house?” The truth is that no human should be exposed to any type of mold for long periods of time because they are all potentially hazardous. However, EuroMaids professionals the chance of this fungus ending human life is incredibly rare under ordinary circumstances.

All mold is classified into three major categories, depending on the degree of harm it may cause:

  • Allergenic: These are harmless to your health and may cause mild allergies such as a blocked nose or skin irritation in those sensitive to mold.
  • Pathogenic: If you have suppressed, underdeveloped, or a compromised immune system, exposure to this mold can pose a significant health risk.
  • Toxigenic: This mold is incredibly toxic, and professionals should take prompt action to remove it.

The best way to prevent mold from forming is to periodically check areas in your home that produce microclimates conducive to colony growth and ensure there are no surfaces or areas that experience consistent dampness.

Below is a basic guide to help you identify different types of mold. Pictures alongside the descriptions should help too, but when in doubt, call the experts. Remember, you should never touch mold with your bare hands and always wear a mask and goggles during the removal process, as inhaled spores tend to thrive in human respiratory tracts.



Acremonium colonies are white, pink, gray, or orange. If found early, their powdery texture will be moist. Generally, this mold thrives indoors under very wet conditions following flood water damage and is commonly found in moist compact areas like drainpipes, window sealants, humidifiers, and cooling coils.

It’s one of the most dangerous house mold types. Its toxicity can cause infection in persons with wound injuries and lead to bone marrow and immune system diseases, as well as brain function impairment. More commonly, it induces hay fever,  asthma, and hypersensitivity pneumonitis.


Alternaria is one of the most common types of house mold, with over 250 species. Indoor Alternaria spores usually originate outdoors and multiply in carpets, wallpaper, textiles, window frames, and HVAC systems. Like all mold, it grows in damp and humid areas, reaching maturity in just five days.

Those with pulmonary diseases, asthma, weak immune systems, and allergies are most vulnerable to this mold. Prolonged exposure to Alternaria has been linked to the onset of asthma in children, while allergies wrought on by its spores are more pronounced in spring and summer. It habitually lingers in the air on dry, windy days and, when inside, can grow under carpeting and inside walls in some cases.



Aspergillus mold starts off white and transforms to green, black, brown, or yellow as it grows, depending on the species. It is an allergenic mold, meaning it is most likely to produce allergic reactions such as asthma attacks, lung infections, and respiratory inflammation.

Its species spread rapidly in low-nutrient areas like damp carpets, walls, doors, windows, and even pillows. This is one of the more common types of house mold found in homes around the world, along with the black and pink mold. It becomes dormant in colder areas but can survive and regrow in warmer weather.


This mold is common indoors in moist, damp, and humid areas like bathrooms, kitchens, tile grout, behind wallpaper, caulking, window frames, textiles, HVAC units, and on painted and untreated wood. Usually pink, brown, or black, Aureobasidium is flat and smooth and becomes velvety over time.

The primary health risk associated with this mold is its ability to cause eye, skin, and nail infections and so should never be touched with bare skin. Because it is not a primary human pathogen, not everyone exposed to it will get sick. Those at greater risk are people with compromised immune systems, babies, and the elderly.



Chaetomium types of house mold can be found on wallpaper, drywall, door and window trim, paper baseboards, cardboard, carpets, and damp paper, making it a concern for libraries, book and paper archives. It has a cotton-like texture that changes from white to gray to brown and eventually black.

This mold mostly causes skin and nail infections. If you have Chaetomium in your home, you may have a serious mold problem, as its spores are larger and heavier than other types of mold. Chaetomium is a sign of constant moisture, so be sure to check any leaky water lines and roofs, and damp basements.


Cladosporium is a mold genus with around 220 species, making it one of the more widespread types of house mold. Most of these allergenic mold colonies appear as black, brown, and olive green and uniquely grow in both warm and cold conditions. Cladosporium thrives in carpets, upholstery, fabrics, under-the-floorboards, and inside cupboards.

Like Chaetomium, it causes allergic reactions to the skin, eyes, nose, and throat, with symptoms such as skin rashes and lesions, asthma, lung infections, and sinusitis. Even though it’s not deadly, it should never be handled directly without protective gear.



Once inside the home, Fusarium mold spreads rapidly from room to room. If you notice it in one area, it’s advisable to examine other areas in your home too. Usually pink, white or reddish-brown, this mold is toxigenic and allergenic, meaning that prolonged exposure may damage the nervous system and potentially lead to hemorrhages and internal bleeding.

This dangerous mold typically grows in carpets, wallpaper, fabric, wood, upholstery, and on any other surfaces that have suffered water damage. Because it requires wet conditions, it’s often found in indoor humidifiers and has a flat, wooly, or cotton-like texture.


Similar to Fusarium, Mucor is a fast-growing mold that’s typically white, grey, or cream-beige, with a cottony texture. With over 50 species, this mold feeds on house dust and can live in carpets, mattresses, and upholstered furniture if moisture levels are high enough.

This strain can trigger respiratory problems and allergic reactions, including coughing, sneezing, a runny or blocked nose, postnasal drip, a sore throat, itchy eyes, sinus headaches, and skin rashes. Mucor is most commonly found in buildings that have suffered flood damage and remain damp.



The Penicillium genus contains over 300 species, including the famous antibiotic Penicillin. Usually vivid blue-green or yellow, it does not typically produce serious toxins but remains a concern for immunocompromised individuals. Allergic reactions in the form of respiratory problems and sore throats may occur in some people.

Penicillium is one of the most common types of mold found in ordinary homes. It can grow on fabrics, old mattresses, couch cushions, carpets, plywood, and even in the insulation inside walls. Any damp building materials and books, boxes, or wood stored in moist basements are potential hazards.

Stachybotrys (Black Mold)

Characterized by black blotches or smears, Black Mold is unique because of its sticky spores that adhere to surfaces that can remain dormant for many years until reintroduced to a water source. While often touted as one of the most dangerous types of house mold, in most cases, it won’t affect or kill an individual.

However, prolonged exposure may lead to nausea, vomiting, bleeding in the lungs and nose. Stachybotrys favors humid microclimates produced by sweating pipes, underneath sink cabinets, in front-loading washing machines, damp cars, as well as nearby roof leaks and windows with condensation.



Trichoderma is one of those bathroom mold types that start out as white or yellow and turn gray or dark as the colony matures. It is commonly found in water-saturated wood, gypsum board, paint, HVAC filters, and even in mattresses. Because this mold attacks wood, it can cause rot, damaging the structural integrity of your home, so proper mold removal is crucial.

People with allergies may experience severe reactions, ranging from asthma to persistent coughing and lung infections. If this mold contaminates an air conditioner, it poses a greater health risk, as it's extremely likely to spread all over the house, so be sure to check your HVAC system regularly.


Ulocladium mold is brown, gray, or black and grows in water-damaged buildings, wet carpets, and surfaces. Unlike the other different types of house mold mentioned, it needs large amounts of water to survive, so if present, it’s a clear indication of severe water damage.

Textually it’s like cotton wool grows rapidly and takes around five days to attain maturity and produce spores. Once inhaled, it may cause allergic reactions like asthma, hay fever, and difficulty breathing. Ulocladium is often found alongside Chaetomium, Fusarium, and Stachybotrys, increasing its potency.

Ulocladium above a floor


While mold is harmful to humans, it is only after prolonged exposure that severe health effects occur, and only in very rare cases is it fatal. It’s impossible to eradicate spores as they are part of the natural environment’s ecosystem; however, keeping your home, and especially the bathroom, clean and tidy, prevents colonies from forming.

Our professional team at EuroMaids will be happy to clean your residential or commercial space to ensure it stays mold-free. Our range of comprehensive cleaning services will make your home, office, or retail space look as good as new! Call us at (630) 737-1080 or click here for a free quote.

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