Most common mold types are widespread and found worldwide. While, the less common ones shown below are usually rare in occurrence. These are about 18 types of mold – less common indoors, but you shouldn’t ignore them.
Rare occurrence of these molds does not mean they are less harmful. Also, some studies show them more prevalent in some regions. And breaking the trend of typical test results. Let’s look at them, one by one.
There are about 20 different species of Absidia. Absidia corymbifera, also known as Absidia ramosa or Mycocladus corymbiferus.
Absidia grows in soil and decaying vegetation. It is also found in grains in some areas. Absidia can travel with wind and dust to enter indoors. Dusty mattress, mats or pot soil are the specific areas where it lives.
This mold grows better in dry environment with little high temperatures. It appears grey or grey-blue in color.
Chrysonilia is one of the fastest growing molds. In other words, you need some immediate action if found inside your house or building. Fortunately, this isn’t one of the very common ones found indoors.
The species named Chrysonilia sitophila is more common in findings. It has a red or pink appearance and usually found on bread which gave it another name “red bread mold”.
Like other common mold, Chrysonilia grows on organic materials. Apart from bread and food, it can also spoil the building materials like drywall and carpet.
There are about 80 different species of Curvularia. It is more commonly found in tropical and sub tropical regions. Curvularia’s occurrence is common outdoors. But it is also found indoors especially with wooden structures.
Some species of Curvularia may be harmful to humans. It affects the skin and respiratory system and it has a potential to infect human heart.
Most species start growing with light color like white or grey. And turns darker brown or black after maturity.
This mold is one of the most toxic human pathogens. The species affecting us is Emericella nidulans also called aspergillus nidulans.
It is usually green in appearance or sometimes dark colored with a green pinch. This mold has a potential to cause variety of allergies and known to cause sinusitis.
Epicoccum mold grows indoors on house plants, dusty carpets and damp drywalls. Also, grows on Air conditioning systems and wet wooden structures. You can find this type of mold in yellow, orange, red or brown color.
Epicoccum is a type of mold found worldwide as it can grow in variety of environment. Same as most other molds, it has its origin in soil and dead leaves. At the same time, unlike most other types, this mold also grows in marine environment.
One form of Epicoccum mold is useful while the other is harmful to humans. One of the most known species of Epicoccum, E. nigrum is a species that produces colored pigments. And this pigment is useful as anti-fungal agents against other fungus! It is also useful in medicine, agriculture and pigment industry.
It is harmful while found indoors. But, not known for causing any major diseases. It can cause allergies or breathing and skin problems.
When found indoors, Eurotium shows close connection to poor ventilation and humidity issues. Buildings like hospitals, hotels and schools sometimes have bigger ventilation issues compared to small house. That’s why, Eurotium is a prime suspect while mold inspectors are reviewing bigger buildings.
The species of this mold usually found indoors are: amstelodami, rubrum, repens and herbariorium.
The mold Eurotium and Aspergillus are closely connected. E. amstelodami (previously known as A. amstelodami) is known for producing bacteria that can cause tuberculosis.
Eurotium develops in dark, humid and less ventilated areas. Their presence is common on furniture, below the carpet, wallpaper and drywall.
This mold is yellow or brown in color and usually found in floors inside the building. Geomyces pannorum is the species which is widespread in northern hemisphere. As it likes to grow in cool habitats.
Although, it is less common indoors, some studies in UK houses found this one as a more prevalent one. Especially during sampling in winter months.
It is classified as Saprophytic fungi, which uses dead plants and animals as a food. Indoors, it may still find the organic material as a food like drywall, carpet and dust mats.
Geotrichum is white in color and starts to grow with tiny white formations. Due to its color and size this mold is difficult to spot in nascent stage. It is usually found in damp areas or water damaged areas of the house.
Geotrichum candidum is the species that is found worldwide. And it is also normal to find them inside the human body as a part of human microbiome.
Being white in color it can easily cheat your eyes, and later when fully grown, it becomes tough to get rid off. Fortunately, this is not a very common one usually found indoors.
This mold may infect your lungs and pose inhalation health risk. It is known to cause a secondary infection with people suffering tuberculosis. And this infection is geotrichosis, a very rare kind of infection.
A fully grown Gliocladium mold will appear green in color. It is a widespread one and found globally. It is one of the fastest growing molds. Gliocladium has a rare occurrence in houses. When found indoors, it is seen on damp building materials.
Health impact on human body by Gliocladium is still a subject of research. And not enough information is available in that regard. Although, some species of this type are under allergenic mold.
It is grey black in color and closely connected to Acremonium. It is not often reported for indoor environments. But sometimes found on water damaged cellulose containing materials.
Not much information is available on this mold. Especially, the health effects on human body.
Memnoniella has a same appearance as Stachybotrys mold. Stachybotrys, which is more commonly known as the black mold.
They grow together, one after another. Stachybotrys is primary colonizer which starts growing first. And then Memnoniella will follow to grow together.
The major building materials affected are drywall and ceiling tiles. because, this mold eats cellulose containing materials.
The health effects of both the molds are similar and both could be dangerous. The Memnoniella mold is riskier due to its tiny structure. Also, due to potential of entering and damaging lungs easily.
They are both considered toxic. Moreover, they may produce the same types of allergic symptoms in humans.
Myrothecium verrucaria is a very strong cellulose eating mold species. In other words, wood and drywall are the favorite food for Myrothecium.
Fortunately, its occurrence inside houses is rare. But rare doesn’t mean never. Some studies reveal the presence of this mold in houses. And any mold once detected, must be eradicated from roots.
Myrothecium verrucaria is a well-known pesticide as it can kill weeds and nematodes.
Have you ever seen an expired lip stick or cosmetic? Probably not. Because, most countries do not require that label, including Canada. You may be wondering how is cosmetic related to this mold?
So, here is the answer. Some studies have found Paecilomyces mold on old cosmetics! It sounds weird but true.
Apart from make up items, it was also found plastic contact lenses. In addition, it was found in wall cavities and synthetic rubber during some past investigations.
Paecilomyces is still a less common mold for indoor environment. But, when found indoors, it is usually isolated from carpet dust, HVAC system, damp walls and floors.
It is one of the fast-growing molds and found in yellow, golden, lilac or brown colors. Recent studies revealed its impact on human health. Especially, by the species known as Paecilomyces (P.) variotii and P. lilacinus.
Soil and wet wood are most favored places for this mold. Surprisingly, it wasn’t first discovered from soil or wood, but it was first found in human body.
It was first discovered from a buttock skin lesion of a man from Boston. Due to its morphology it was named Phialophora meaning “shallow cup bearer”.
Phialophora needs high moisture environment (more than 90% Relative Humidity) to grow.
Studies relate different moisture levels required to the growth of each mold type. There are three moisture levels in which different type of mold grows. And they are, Low moisture (less than 80% RH), Intermediate (80-90% RH) and High (more than 90% RH).
Wood is good for moisture balances in buildings. But the molds like Phialophora use this property of wood, to grow in it. One of the species Phialophora fastigiata is common indoors. It has been found from wood panels in Sauna, wet windowsills of wood and sometimes from humidifier.
Some species of this mold can cause blue stains in wood. Although, The Canadian Wood Council confirmed that those blue stains do not affect the wood or human health.
Not much is known or reported about health impact due to Phialophora mold. But whenever detected, a professional mold removal agency should address it.
Phoma is primarily a plant pathogen. It is known to spoil food and plants. And less harmful to humans.
Indoors, it is thriving on paint and caulking. The caulk on shower tubs or under the sink may show up dark brown or black stains due to Phoma.
It doesn’t mean that black stains you see on these locations are only due to this mold. It could be some other type of mold with black color!
Phoma also grows on window frames, wall papers, bathrooms and house dust. Phoma’s appearance is red, orange, green, grey, dark brown or black. Depending upon the maturity level.
The most found indoor species of Phoma are, P. glomerata, P. porporum and P. macrostoma.
Impact on human health due to Phoma is not very much known or reported. Most studies confirm it is less harmful compared to many other mold types found indoors.
The most common species found indoors are 1. Scopulariopsis brevicaulis 2. S. gracilis and 3. S. brumptii. Scopulariopsis brevicaulis affects the food with high protein. For example, cheese and meat.
Carpets, damp walls, wallpaper and paint are most affected areas by Scopulariopsis mold growth.
The species Scopulariopsis fimicola is also known as white plaster mold. As it appears like white colored Plaster of Paris.
This mold can also affect commercial mushroom production but not very common indoors. If found indoors they are usually brought into house by compost or dust.
There is less known about any severe health impact of this mold. Although, some cases were reported in past. One of them was Scopulariopsis growth in patient’s thigh. And that lead to critical health problems.
You will need an expert mold detection agency to confirm the growth of this mold in the house. As it may not be visible to naked eyes all the time.
The most favorite spot of Sistotrema is building part made of wood. Especially the thin gaps due to cracks or joinery. This is probably the reason it is most found in doors and windows. Eventually, degrading the structural integrity of building components.
As field experts have insisted it several times, any signs of any kind of mold indoors must be treated as alarming. It may not affect human health directly, but it can affect the health of the building like this one!
Wallemia is a xerotolerant mold. Which means it can survive in very dry conditions. That makes it unique from other type of molds.
Due to its ability to survive in dry conditions, it is usually found in house dust. Moreover, it has a yellow- brown dusty color which easily blends with house dust and not very easy to detect. The most common indoor species is Wallemia sebi.
Apart from house dust, it is also found on foods having high amounts of sugar or salt. Such as jam, cake and salted fish.
Wallemia sebi may cause allergic reactions and respiratory issues. It is believed to worsen asthma problems. However, its direct relation to asthma is still not confirmed.
Hope these details on “18 types of mold less common indoors” will help you understand a little more about molds. Also, to realize that mold removal is certainly not a DIY thing and you need a licensed professional to help you.
Read more on mold:
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This article is more on awareness for mold removal. We are not claiming to be expert mold advisors. Any information on health impacts of mold must not mean a health advice from us.
Sources and acknowledgements:
This article is an attempt to make the understanding of mold- a little simpler and easier. We also acknowledge the use of some information from following sources. And we are very thankful to those publishers.
1. NCBI: National Center for Biotechnology Information : According to NCBI, someauthors directly relate fungal contaminated indoor environments to illness. But, a close examination by experts reveal a confusing picture not fully confirming it!
2. MBL: Mold & Bacteria Consulting Laboratories.
3. Global Indoor Health Network, Inc.
4. WHO Guideline.
5. Residential Indoor Air Quality Guideline: Moulds (Government of Canada / Canadian Mold Guideline)