12 Types of Mold That'll Make You Want to Deep-Clean Your House ASAP

Prolonged exposure to black mold has been linked to respiratory problems, skin irritation, and other health problems. People with asthma or immune system diseases may face more severe reactions, including asthma attacks or lung infections.

It typically grows on water-damaged materials such as drywall, wood, and other building materials rich in cellulose. This mold thrives in damp environments and often gives off a strong musty odor.

Aspergillus mold is among the most common indoor molds and appears in many colors, including green, white, and dark brown. It is commonly found in air conditioning systems, house dust, and on organic substances.

This mold can trigger mold allergies and asthma symptoms. In more serious cases, especially with indoor exposure in people with weakened immune systems, aspergillus mold can lead to pulmonary infections or other lung infections.

Cladosporium is another of the most common molds found indoors and outdoors. It grows on dead plant material, fabrics, and wooden surfaces—especially in cool, damp environments like basements or window frames.

It is considered an allergenic mold and can cause allergic reactions such as a runny nose, skin irritation, and respiratory problems. It can still affect indoor air quality and cause health effects when mold growth spreads.

Alternaria is often found in damp indoor environments after water damage. It commonly appears as dark patches and spreads quickly across wet surfaces.

This mold is a major trigger for mold allergies and asthma symptoms. Indoor mold growth involving alternaria can worsen asthma attacks and contribute to ongoing respiratory problems, especially in sensitive individuals.

Penicillium is known for its suede-like texture and blue-green or white coloring. It grows on water-damaged materials, carpets, and other building materials where moisture persists.

It spreads easily through mold spores in indoor air and can contribute to mold exposure that leads to allergic reactions and sinus issues. A persistent musty odor is often a clue that penicillium mold is present.

Chaetomium mold is commonly found in buildings with long-term moisture problems. It thrives on cellulose-rich materials such as drywall and paper products.

This mold starts as a white mold and darkens over time. It is associated with water-damaged materials and can pose health risks, including skin infections and nail infections.

Fusarium grows in a wide range of conditions and is often found in soil, plant material, and indoor environments affected by water damage. Unlike some other molds, it can grow even in cooler temperatures.

It is considered both allergenic and pathogenic, meaning it can cause allergic reactions as well as infections—such as skin and nail infections—or more serious issues in people with compromised immune systems.

Trichoderma is commonly found on wet building materials and wooden surfaces. It spreads quickly in damp environments and often signals a larger moisture control issue.

Some species of trichoderma produce mycotoxins. It can also damage wood, affecting structural components of buildings.

Ulocladium often appears in homes with a history of water damage. It grows on wet surfaces such as painted walls, window frames, and other building materials.

This mold requires constant moisture to survive, so its presence usually points to an ongoing moisture problem. It can contribute to allergic reactions and poor indoor air quality if left untreated.

Mucor is a fast-growing mold commonly found in house dust, carpets and HVAC systems. It thrives in damp environments and spreads rapidly across organic material.

While often less harmful to healthy individuals, mucor can cause serious health risks such as pulmonary infections in people with weakened immune systems. It also contributes to overall indoor mold growth and poor air quality.

Acremonium is typically found in humidifiers, cooling coils, and other parts of air conditioning systems. It starts as a moist mold and gradually turns powdery.

It can contribute to indoor exposure that leads to respiratory problems, skin irritation, and other health effects. Because it often hides in systems that circulate air, it can spread mold spores throughout a building.

Aureobasidium commonly grows in bathrooms and kitchens on damp surfaces such as tile grout, caulking, and window frames. It may appear pink, brown or black.

It is usually considered an allergenic mold but can still cause skin irritation. Like many other molds, it signals excess moisture and poor ventilation.

Green mold and brown mold are informal terms that group several mold species based on color. Green mold often includes aspergillus and penicillium, while brown mold may include stachybotrys or other molds found on decaying organic material.

These molds are commonly found on food, plants, and building materials. While not all are toxic, many can still pose significant health risks, especially when mold cleanup is delayed and indoor mold growth spreads.

You can often smell mold before you see it, thanks to that characteristic musty odor. Visible signs include discoloration on walls, ceilings, or other building materials. Still, mold found behind walls or inside systems may require mold testing.

To prevent mold, focus on moisture control:

If mold growth becomes widespread, a professional mold removal company can handle mold cleanup safely. Professional mold remediation helps limit the spread of mold spores and reduces long-term health risks.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.