13 Types of Mold in Homes that You Probably Unaware Of

Like most fungus, there are all kinds of mold that can range from pretty harmless to deadly toxic. In this post, we are going to reveal the 13 most common types of mold seen in our home. You will learn about each mold health effects, where to spot them and ways to deal with it. Some of the facts might be particularly useful while others are bizarre even to begin with. If you have not seen a brown color mold or have no idea which type of mold can grow in warm and cold condition, start here.


Image by Wikipedia

1. Alternaria

  • Rarity –  (Very common)
  • Typically found – Shower, bathtub, sink, leaky pipes, plant soil, wet object
  • Health risks – Allergic reaction, hay fever, respiratory infection
  • Harmful level –  (Low – Hazard Class B)

Arguably the most common bathroom mold types. Alternaria is often seen underneath a sink, wall, shower curtain, or bathtub. It can also grow on damp objects like carpet, boots, ventilation or windows frame. You can identify the mold with its gray-green and black color patch.

Not all species of Alternaria are harmful, some would only cause mild irritation. When we inhaled Alternaria mold, the fungus will deposit inside our nose, mouth or upper respiratory tract. This can trigger allergic reactions like cough, sinus to the more severe asthma, hay fever. People with immunocompromised (impaired immune system) like AIDS patients are more prone to the mold attack.

Now you know: Alternaria has an ovoid tapering, club-shaped that is only viewable under a microscope.

Image by Aspergillus Web

2. Aspergillus

  • Rarity – (Very common)
  • Typically found – House dust, air conditioning, heating ducts, insulation, bathroom, basement, food
  • Health risks – Respiratory infection, aspergillosis, allergic reaction
  • Harmful level –  (Medium – Hazard Class A)

Aspergillus is a tough allergenic mold. It can survive on outdoor (decaying leaves, compost piles, house dust) and indoor (air condition, heating ducts, insulation). There are around 200 species of Aspergillus and only 40 of them are harmful to human. Depending on the species, Aspergillus shape varies from spore, flask, to dome structure. Colors can be yellow-green, purple-olive or even grayish-blue.

Aspergillus is not particularly harmful and rarely cause any infections to those with a strong immune system. For those with a weakened immune system like an asthmatic person, it can trigger an asthma attack. On a bad run, it can lead to respiratory problems plus infamous cancer-linked Aspergillosis. Aspergillosis is a potentially fatal fungal infection that grows inside the lungs. The fungal spread across the brain, heart or kidneys via the bloodstream.

Now you know: Aspergillus niger, Aspergillus terreus, Aspergillus flavus is the more common species of the genus Aspergillus.

Image by Medical News Today

3. Cladosporium

  • Rarity – (Very common)
  • Typically found – Fabric, upholstery, carpet, cupboard, cabinet, floorboard, bathroom
  • Health risks – Skin allergies, eczema, respiratory infection
  • Harmful level –  (Low – Hazard Class B)

Cladosporium is also a common outdoor mold found in fall leaves or dead herbaceous. The fungus can travel and grows inside your home through HVAC system or open windows. The allergenic mold has a pigmented color from pale olive-green yellow to light brown. Another characteristic of Cladosporium is it can thrive in warm and cold conditions. This makes it perfect for sofa upholstery and wood furniture with heat retention.

Most species of Cladosporium mold has little health risks to human. Exposing and breathing to Cladosporium may cause skin allergies like rashness or dermatitis. In rare cases or people with a weakened immune system, it can aggravate respiratory diseases. Regularly clean HVAC system, aircon is the best way of reducing the allergenic mold in your home.

Now you know: One of the larger genus of fungi, most Cladosporium species has an ellipsoidal to cylindrical shield-like shape.

Penicillium Chrysogenum
Image by daniela beckmann

4. Penicillium

  • Rarity – (Very common)
  • Typically found – High dampness area including food, wallpaper, insulation
  • Health risks – Respiratory infection, allergic reaction
  • Harmful level –  (Low to high Hazard Class B)

Penicillium is one of the easier molds to spot due to its association with a damp environment. Often grows with other types of mold, it can be found in wallpaper, adhesive, duct insulation, or upholstery. Penicillium has a spore shape with brush-like top. Most species carrying a greenish, bluish or somewhat yellowish color.

Not all Penicillin is dangerous to our health. Only a handful of toxigenic mold species carrying mycotoxins substances. The chances of breathing to the toxigenic type are much higher as the spores can easily become airborne. Asthmatic person, infant or elderly are on a higher risk group of receiving the infection. A HEPA air purifier can capture the airborne toxic before anyone else.

Now you know: Penicillium Chrysogenum fungus extract is used to made antibiotic penicillin. Penicillium is also used to create blue cheese.

Stachybotrys Chartarum (Black Mold)
Image by Kristopha Hohn

5. Stachybotrys Chartarum (Black Mold)

  • Rarity – (Common)
  • Typically found – High dampness area including wall, ceiling, wood, basement
  • Health risks – Respiratory infection, allergic reaction, skin allergies, vision impair, physical and mental problems, reproductive system troubles, circulatory and neurological problems
  • Harmful level –  (High – Hazard Class A)

Stachybotrys Chartarum is the scientific name but most people will refer to it as BLACK MOLD. It is the most notorious types of mold found in home that should be dealt with immediately. This slimy, greenish-black mold is hard to miss as it grows in patches. You can often spot the black mold in the basement, drywall, ceiling, shower or underneath a sink.

Black mold produce mycotoxins chemical that is harmful to our body. On short exposure, you might experience symptoms like stuffy nose, cough, watery eyes, skin rash or headache. Temporary health effects include memory loss, fatigue, mood swing or depression. Prolong exposure will lead to lung inflammation, liver damage, infertility (women), and death. Other black mold health effects include abdominal pain, eye damage, or hearing loss.

Now you know: The most common species from its genus is Stachybotrys chartarum or Stachybotrys atra, Stachybotrys alternans, and Stilbospora chartarum.


6. Acremonium

  • Rarity – (Common)
  • Typically found – Drywall, insulation, draining pipes, HVAC system
  • Health risks – Respiratory infection, allergic reaction, skin allergies, vision impair, physical and mental problems, reproductive system troubles, circulatory and neurological problems
  • Harmful level –  (High)

Acremonium is a pungent smelling, toxigenic mold that evolves from small moist to a powdery texture. It is either colorless or light in gray, pink or whitish color. Often found in hard to locate places like drywall, insulation, air conditioning pipes or HVAC system. Is not easy to identify Acremonium due to its small size and can grow alongside other types of mold.

What makes Acremonium harmful is the release of mycotoxins toxic. A carcinogen substance capable of causing cancer in living tissue. The toxic will also cause many other side effects mirror to black mold. Worst case scenario: autoimmune disease, pulmonary edema, abnormal liver, or neurological damage.

Now you know: Despite close to 100 different species, Acremonium mold is even more uncommon than Stachybotrys.

Image by Water Damage Advisor

7. Aureobasidium (Pink Mold)

  • Rarity – (Common)
  • Typically found – Behind wallpaper, wall paint, wooden surface, windows frame
  • Health risks – Skin allergies, allergic reaction, eyes infection
  • Harmful level –  (Low – Hazard Class B)

Aureobasidium is a ubiquitous, slimy indoor mold that can be found everywhere. It started as a creamy, pink color before turning into darkish, dark brown similar to black mold. Thrive on damp places, you will find Aureobasidium behind wallpaper, wall paint or underneath wooden furniture.

Aureobasidium is less hazardous and poses little threat to humans other than allergic reactions mainly to skin or eyes. Still, never have direct contact with the mold without wearing a mask or gloves. Hire cleaning professionals if you are too afraid to deal with it.

Now you know: Aureobasidium pullulans are the most known type within its approximately 14 genus species.

Image by Wikipedia

8. Chaetomium

  • Rarity – (Common)
  • Typically found – High dampness area including wall, wood items, cupboard, basement, food
  • Health risks – Skin allergies, allergic reaction
  • Harmful level –  (Low – Hazard Class C)

A notorious and common indoor mold that is known for its ability to destroy items. Chaetomium is actually more damaging to household materials than causing infection to humans. The strong musky odor will definitely alert you of its presence. Typically found in water-damaged materials from flood or leaky pipe. It can also grow rapidly in drywall, plywood, concrete, or basement. Fortunately for us, Chaetomium needs chronic moisture condition to grow. If you see patches of mold that smells and overtime change its color from whitish gray to brown-black, it’s Chaetomium.

Chaetomium pose little health risk if is in low concentration level and airborne form. In some cases, it may cause a skin rash, watery eyes or itchiness that will eventually go away once you solve the indoor moisture issue. Start checking the HVAC system or piping on any leakage as those places are popular breeding ground.

Now you know: Chaetomium has a perithecia (flask-shaped) body that is only viewable through a microscope.

Image by AgriLife

9. Fusarium

  • Rarity – (Common)
  • Typically found – Soil, plant, wallpaper, drywall, carpet, upholstery, wood flooring
  • Health risks – Skin allergies, allergic reaction, nail infection
  • Harmful level –  (Low to high – Hazard Class A)

Fusarium is a ubiquitous species that can be allergenic or toxigenic mold. You can differentiate it from other molds by its unique pinkish/ red, and white patchy colors. Like Cladosporium, Fusarium can survive and even grow at cold temperature. Children, asthmatic or recovering person are advised to stay far away from the mold.

The allergenic Fusarium species post little health effect other than allergic reactions. Expect rashness on the skin, running nose, cough to bloodshot eyes. The few toxigenic species that are harmful to human can bring lung diseases like Pulmonary edema or Pneumonitis. Discard food, objects that are infested with mold is the quickest and the best course of action.

Good to know: In the agriculture world, Fusarium is becoming a nuisance that often grows in soil or plants and damages the crops.

Image by WiseGEEK

10. Mucor

  • Rarity – (Common)
  • Typically found – Soil, plant, HVAC systems, air conditioning, carpet, decaying food
  • Health risks – Allergic reaction, mucormycosis
  • Harmful level –  (Low to high – Hazard Class A)

Mucor can be seen settling down on soil, plant, decaying leaves. Through the power of wind, the mold will flow into our home and landed on high condensation places like air vent. It’s hard to separate Mucor from other types of mold even though it has a unique white, grayish color and apical shape with soft fluffy texture.

Mucor is known for its fast-growing pace which can be nasty if you have unattended leakage. With around 50 types of species, most are harmless other than triggering mild allergies. In rare cases, it can lead to serious infection call Mucormycosis. A fungal disease that can spread across the whole body via inhaling or skin cuts. Depending on the types of disease you have been infected, Disseminated Mucormycosis is the most critical of them all. It can resulted in fever, mental disorder and life-threatening situation.

Good to know: Cutaneous Mucormycosis is the scientific name for skin inflammation. Rhinocerebral for eyes, nose or brain damage. Renal for kidney failure, Gastrointestinal Mucormycosis for abdominal pain, and Pulmonary for lung infection.

Image by Reddit

11. Trichoderma

  • Rarity – (Common)
  • Typically found – High dampness area including wall, gypsum board, wood products, carpet
  • Health risks – Allergic reaction, respiratory infection
  • Harmful level –  (Low to high)

A very common outdoor mold and equally common in-home mold. Trichoderma is a non-pathogenic mold that can be seen in green color patches with other types of mold. You will often find Trichoderma in damp area e.g. wall, gypsum board, wood cabinet, or carpet. Trichoderma is also known for its anti-fungal ability where the residues would protect plants from other fungal diseases.

Most Trichoderma are on the mild side other than causing mold allergic reactions. The one you have to fret is the Trichoderma aggressivum/ harzianum species. It is toxigenic thus it will produce the poisonous mycotoxins chemicals. Health hazard includes heart inflammation, pulmonary edema to abnormal liver.

Good to know: There are 5 types of Trichoderma genus (Pachybasium, Longibrachiatum, Trichoderma Saturnisporum, Hypocreanum) and approximately 89 recognized species.

Image by assuredbio

12. Ulocladium

  • Rarity – (Common)
  • Typically found – Water-damaged items including gypsum board, wallpaper, wood material, tapestries, other upholstery
  • Health risks – Allergic reaction, skin allergies, hay fever
  • Harmful level –  (Low – Hazard Class C)

Ulocladium is ubiquitous, in house mold that often grows together with other molds. It characteristics include dark grayish, black color and medium to fast growth rate. Ulocladium has a very high water requirement than other strains of molds. It will thrive after a flood where many household items would receive a sustainable amount of water damage. You will typically find the fungus in gypsum board, wall, basement, or upholstery.

Ulocladium might not have the devastation power of black mold, it can still trigger symptoms from cough, running nose to the more severe hay fever. People with impaired immune system stand a higher risk of subcutaneous tissue infections.

Good to know: The genus Ulocladium has two active species; Ulocladium chartarum and Ulocladium botrytis. There are approximately 20 species of reported.

Serpula lacrymans
Image by constantinedd

13. Serpula lacrymans

  • Rarity – (Uncommon)
  • Typically found – Water-damaged items including gypsum board, floorboard, wallpaper, wood material, tapestries, upholstery
  • Health risks – Allergic reaction
  • Harmful level –  (Low)

Serpula lacrymans aka building cancer is the usual in-home mold you would encounter. It is infamous for its building destructiveness than its toxicity to human. It can damage wood items known as dry rot (wood decay) to the extent of masonry materials. When you spotted the distinguish red, brown, gray or black patches of mold, very likely the damage is done and is irreversible.

As we mentioned earlier, one should not be too alarmed when spotted Serpula lacrymans. Only children, elderly and sick person stand a higher risk of mold-related illness. Mold contaminated items that are beyond repair should be clear out before the fungal start spreading. Hire a renovator or carpenter to remove and replace the damaged part.

Good to know: Serpula lacrymans is a basidiomycete in the order Boletales.

Mold is a tough organism that can survive both the indoor and outdoor environment. With at least 100,000 different types of species, mold comes in different sizes, shapes, and colors. To make it easier, the mold will be categorized to either Allergenic, Pathogenic, or Toxigenic based on their toxicity. For ordinary folks like you and me, we typically split them into 2 groups. a) The Good, beneficial mold use in medicine, food (cheese in particular). b) The Bad, stinky mold that is adverse to our health when exposed. There are many mold test kit available online to check you are dealing with. Upon confirming the type, getting rid of the mold should be done at the quickest possible time before it starts spreading.

3 Types of Mold by Health Effects

As alluded earlier, all mold species will be categorized into 3 types:

  1. Allergenic - mildest level that only affects people hypersensitive to allergies or asthma. Most people that unintentionally inhaled to these type of molds would have little to none side effects. Allergic rhinitis is the most common allergic reaction associated with Allergenic.
  2. Pathogenic - also known as opportunistic pathogen mold. It can cause infection to an infant, children with a weakened immune system or people who are immunocompromised. Healthy people that exercise and eats right would have little to fear on pathogens species.
  3. Toxigenic – The type of mold you do not want to mess with. It produces chemical substances called mycotoxins that are known to attack other living organisms. Since the toxic can travel through airborne, you can get exposed to mycotoxins from ingestion, inhalation or skin contact. Pro-long exposure will often bring in serious illnesses that can be fatal.

Other Mold Types That Can Be Found in Homes


3 Hazard Classes of Indoor Mold

In general, indoor mold is tag into 3 different classes based on the health risk factor. Hazard Class A is the most dangerous type that will have a direct impact on our health. Follow by Hazard Class B, and lastly Hazard Class C that has a much lesser impact on our health. Below are some examples of indoor fungi associated with the group.

  • Hazard Class A - Stachybotrys, Aspergillus, Fusarium, Aspergillus, Geotrichum.
  • Hazard Class B - Aureobasidium, Penicillium, Alternaria, Cladosporium.
  • Hazard Class C - Chaetomium, Ulocladium, Wallemia.

How to Get Rid of Mold In-house Naturally

Detergent, bleach, ammonia, or talcum powder are few of the unnatural ways of removing mold. It works but why would you want to inhale to more chemicals when a natural ingredient can do the job? Below are 10 proven, non-toxic products that are safe and effective in getting rid of mold.

  1. Vinegar
  2. Baking Soda
  3. Grapefruit Seed
  4. Tea Tree Oil
  5. Cinnamon essential oil
  6. Oregano essential oil
  7. Thyme essential oil
  8. Clove essential oil
  9. Lemon Juice
  10. Vodka (Yes, the drinkable one)

Keep in mind though, most of the above method will only kill off surface mold that can be seen. Anything that is hidden beneath porous materials like wood is untouchable. you might need to toss away the damaged part or consider a renovation. Otherwise, consider hiring a mold remediation expert to do a complete cleanup.

Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.