It’s every homeowner’s nightmare: Mold infestation! But how do you tell the difference between harmless mold and species that are dangerous for humans?

This quick guide runs through seven of the most common species of household mold. If you spot these species growing on your pool deck, siding, or roof, it’s time for a cleaning! Give us a call at (904) 747-6DPW (4379) or fill out our contact form for your free estimate for power washing, soft washing, and mold and mildew removal.


black mold is the most dangerous mold for your home
Image Credit: Molekule Science

1. Stachybotrys (“Black Mold”)

What it is: Even if you haven’t heard of stachybotrys, you’ve probably heard of black mold. Black mold is one of the most dangerous species of mold for humans–and it’s commonly found inside homes and office buildings.

What it looks like: We call stachybotrys “black mold” because it appears as a dark, fuzzy stain. It’s usually black, but it can be dark green or gray as well.

How it hurts your home: When exposed over time to black mold, humans can develop dangerous lung issues. Black mold is particularly dangerous for kids, as their lungs are still developing and are more susceptible to this mold’s ill effects.

Aspergillus is a household mold that's dangerous for humans
Image Credit: Water Damage Advisor

2. Aspergillus

What it is: Aspergillus is a wood- and water-loving mold. Most commonly found on wooden surfaces, aspergillus can also collect on tile or grout.

What it looks like: This type of mold typically appears as gray or green flecks, usually collecting on wooden surfaces.

How it hurts your home: Aspergillus is a pretty common allergen. With 20 species in total attributed to this mold family, this pesky growth can aggravate allergies, asthma, or hay fever symptoms. It’s important to get rid of quickly because it lets off mycotoxins, which can be dangerous for people with compromised immune systems.

Penicillium is a dangerous household mold that grows on humans' food
Penicillium mold on tangerines. (Image Credit: Science Photo Library)

3. Penicillium

What it is: Penicillium is a common household mold that can be both beneficial and harmful. Some species of penicillium produce–you guessed it!–penicillin, which is used in antibiotics. However, certain strains of penicillium mold (like those that collect on food) can be harmful for humans.

What it looks like: This blue-green mold collects on food, particularly citrus fruits or foods that have been improperly stored. It appears as the fuzzy blue coating we’ve all seen on clementines we’ve left out too long!

How it hurts your home: Some species of penicillium are actually helpful for humans: The species that produce penicillin, for example, have been used in the study of antibiotics for years. However, constant exposure to penicillium (on food, for example) can aggravate allergy symptoms and produce mycotoxins that are dangerous for the kidneys. Yuck!

Chaetomium is a mold species that is dangerous for humans
Image Credit: Aerotech Laboratories, Inc. / Anthony Plumbing, Heating and Cooling

4. Chaetomium

What it is: Chaetomium is a water-loving mold typically found in places that have seen significant water damage. It brings that musty, dank odor that we associate with waterlogged wood or leaky basements or drywall.

What it looks like: Chaetomium has an almost crystalline look to it. This blue-white mold collects on moist surfaces, like water-damaged wood or drywall.

How it hurts your home: This form of mold is one of the more dangerous types for humans. Besides the usual allergy-inducing worries, it’s been linked to genetic diseases, neurological damage, and even some types of cancer! If your home has been damaged by water, keep an eye (and a nose) out for chaetomium growths. These need to be removed right away.

Alternaria mold is dangerous for humans
Image Credit: AOA Cleaning and Restoration

5. Alternaria

What it is: This outdoor mold species can take over sidings and roofs, or find its way inside your home to aggravate your allergies. Alternaria is a plant pathogen, which means it affects leaves and bushes as much as it affects humans. When picked up by a breeze, alternaria spores travel to the next warm and humid location before growing into a problem.

What it looks like: Alternaria can be green or dark brown (close to black) that appears as the typical “mold stain.” On plants, you’ll find alternaria popping up as leaf spots and other discoloration. On pool decks, roofs, and outdoor sidings, you’ll see alternaria forming as a patch of brownish muck.

How it hurts your home: While alternaria isn’t toxic or deadly, it can be a major aggravation for allergies and asthma. Over time, like many molds, prolonged exposure to alternaria can cause serious health issues in children, the elderly, or people with health complications.

Fusarium is a moisture-loving mold that's dangerous for humans
Image Credit: Contractor Quotes

6. Fusarium

What it is: This plant-based mold typically impacts plants and soil, but it can also cause a series of infections in humans. Typically found in moist areas, like around window frames, fusarium is a common enemy of home gardeners and DIY experts alike. In fact, some species of fusarium have even been used in biological warfare!

What it looks like: Typically a pale yellow or white (but sometimes appearing in brighter shades of pink, yellow, or brown), fusarium collects on dry wall, carpets, wood floors, and water-damaged surfaces.

How it hurts your home: Fusarium has been linked to the outbreak of many infectious diseases. It’s also a culprit for nail and eye infections, allergy exacerbation, and asthma attacks. Plus, an untreated fusarium infestation can cause structural damage to your home!


Trichoderma is a wood-growing mold that can be dangerous for structures
Image Credit: Project Noah

7. Trichoderma

What it is: Trichoderma is one of the most common species of indoor mold. It’s typically found on wood surfaces because wood is its favorite food: Over time, trichoderma can eat through wood, threatening the structural integrity of decks and wood patios!

What it looks like: This fuzzy green mold looks a lot like lichen, which is why it’s so easy to mistake for a friendly growth if you see it on trees or on wooden outdoor structures.

How it hurts your home: Trichoderma eats straight through wood, which makes it a major pest when it comes to maintaining the structural integrity of your deck or patio. Plus, like most molds, extensive exposure to trichoderma is linked to allergy issues, asthma, and other respiratory problems.


What do I do if I find mold around my home?

Give us a call! The team at Diamond Power Washing and Maintenance is here to help remove mold and mildew from your outdoor areas. We can also re-seal pavers or waterproof your outdoor areas to keep mold growths from coming back. With pressure washing and soft washing treatments, we can nip a mold infestation in the bud before it has a chance to threaten the health of your home or family members.

Give us a call at (904) 747-6DPW (4379) or email to schedule your FREE estimate!

24,503 Thoughts on “Dangerous mold: Can you spot it skulking in your home?”