Mold species – what molds are and what they look like

Mold is sometimes talked about as if it’s all the same. In reality, there are thousands of species of mold, and some can affect your health more than others. It can be confusing because any one species can affect people differently. 

First, some people are allergic to specific mold types, while other people are not. Second, those with compromised immune systems are at greater risk of serious infections. Finally, people with respiratory system illnesses or respiratory problems are at risk for various negative health effects

mold species

Further confusing things, people who are affected will be affected in varying degrees. 

When you’ve found mold, you’ll want to identify which type it is to determine the potential health hazard being dealt with. When mold is suspected but not confirmed, the next step is verifying its presence with a mold test kit or contacting a mold removal professional. Once confirmed, several mold removal products are available for both professional and DIY use.

Mold Categorized by Health Hazards

Allergenic Molds

If you have allergies or asthma, these are the molds that may cause problems for you. When you are exposed, your body may overreact and cause you to experience an inflammatory response. About a quarter of people are sensitive to these molds, but people without allergies can tolerate them in small quantities.

Pathogenic Molds

Most healthy adults will not be adversely affected by these molds, as they can fight off pathogens. These molds can affect infants, elderly adults, and people with weakened immune systems.

Toxic Molds

Toxic molds are dangerous to all humans. They produce poisonous chemicals called mycotoxins, which can cause reactions ranging from temporary irritation to long-term illness. You can come in contact with the mycotoxins through ingestion, inhalation, or skin contact.

Important: Wearing a mold respirator and protective clothing is recommended when working in areas where mold has taken hold.

Common Toxic Mold Species


Alternaria includes many species, and is one of the most commonly found toxic molds. If you inhale the spores from this mold, you may develop asthma or hay fever. You may see it in damp and dark areas inside or outside the home.


One of the most difficult types of mold to eliminate, ascospores can live on dried out material until wet conditions return. This mold is often found in laboratories, where it is spread by infected animals. It can cause problems with hair and nails.


Wooden surfaces are where you’ll find this mold, and it will appear as green or grey flecks. This is a dangerous mold, capable of causing hay fever, lung infections, and even serious asthmatic symptoms. It is particularly troublesome for immune-compromised individuals.


If you see a black or pink spotty substance, it could be this type of mold. It turns to a dark brown when it matures, and is often hiding behind wallpaper or in water-damaged carpet. This mold can cause eye, nail, and skin infections.


Often spread on the wind, the mold usually grows outdoors in forests and gardens. Open doors and windows can bring the spores into a home, but it rarely grows indoors. Asthma and hay fever can result from exposure.

Air Purifiers and Mold: Many consumer air purifiers for mold are capable of removing airborne mold spores. But, for industrial mold remediation professionals use a combination of air movers and air scrubbers are required.


This gray/white mold becomes dark green as it matures, which takes less than a week. It can be found indoors in water-damaged carpets or houseplants. Outdoors, you’ll find it on grass or soil. When the spores are inhaled, asthma, coughing, stuffy nose, and wheezing can result.


The spores from this common mold have been associated with breathing difficulties and watery eyes. It is often confused with black mold as they thrive in similar environments. You may notice a musty odor when you find it under carpets or behind wallpaper.


Brown or dark green in color, this mold can survive in warm or cold areas. Look for it under floorboards or in fabrics. Allergic reactions to the spores can include itchy eyes, skin infections, sore throat, and runny nose. It has been linked to asthma, lung infections, and sinusitis.


Pink, reddish, or white, this mold can live in colder areas. Look for it on food items or water-damaged materials such as carpet or wallpaper. Reactions to fusarium can lead to mild symptoms like itchy eyes, itchy skin, runny nose, or sore throat. Prolonged exposure can cause more serious health concerns of bone infections, brain abcesses, internal bleeding, or nervous system damage.


Powdery white in appearance, this mold spreads quickly in temperate climates. The spores spead easily in the air and can cause chronic headaches, itchy eyes, and fatigue. It’s even been associated with pulmonary infections and tuberculosis.


This type is also known as black mold, and is one of the more harmful species. It is usually found inside a home. It can be hard to find because it often grows behind walls and under ceilings. The mycotoxins released by this species can cause bleeding in the lungs, which can be fatal to pets and infants. When viewed under a microscope, you can see that the spores are released in chains.


Some species of Penicillum are beneficial, and can be used to produce cheeses and medicine. Other species can trigger allergies which are troublesome for individuals with weakened immune systems.

Serpula Lacrymans

Found outside or inside, this mold feeds only on wood. It is yellow in appearance and can cause dry rot.


This is a type of black mold, causing similar health hazards as Memnoniella. It differs from Memnoniella when viewed under a microscope. The spores released by Stachybotrys are in clumps rather than chains.


White with green patches, this allergic mold prefers moist areas. Some of the five subspecies have been known to cause liver and pulmonary infections. This mold can destroy paper products, textiles, and wood. This can cause rotting buildings.


Found in wet or water-damaged areas, this black mold is common in basements, bathrooms, and kitchens. It has been associated with hay fever and skin infections. Continued exposure can lead to asthma-like symptoms.

Identifying Mold by Color

One of the easiest ways to narrow down the type of mold you’re dealing with is to note its color.

Brown Mold

This group includes mold ranging from dark yellow to tan or brown. These types look like dark spots on surfaces. Some common brown mold species are Aureobasidium, Chartarum, Pithomyces, and Stemonitis. Brown molds are not harmful to most people, but their spores can cause health issues for individuals with asthma or allergies. Brown molds can cause damage to structures.

Black Mold

This category includes mold that looks black, dark green, or gray. You may find black mold in basements, bathrooms, and kitchens because they grow in places with warmth and moisture. Black mold is usually problematic, as it releases toxins that cause allergic reactions. The symptoms you may notice include coughing, itchy eyes, itchy skin, stuffy nose, and wheezing. In some individuals, black mold can cause more serious symptoms such as breathing difficulty, fever, exhaustion, and headaches.

Green Mold

Green mold can get its color from the material they eat or the area they live in. There are thousands of species of green mold, and most can cause serious health risks. The mycotoxins they produce can cause allergic reactions including coughing, itchy skin, sneezing, and watery eyes. Some commonly found green mold species are Aspergillus, Cladosporium, and Penicillium.

Orange Mold

These species form tiny spots when they start to grow. When mature, the tiny spots become slime. Orange mold is often seen in bathrooms because it thrives on humidity. It can also grow on food items like bread, cheese, and yogurt, causing them to spoil. Though it is not life-threatening, orange mold can cause damage to structures.

Pink Mold

Pink mold thrives in humidity. For this reason, pink mold is often found in kitchens and bathrooms. Pink mold will be more prevalent during humid times of the year.

White Mold

You’ll usually see white mold in buildings with water damage. It can be hard to identify because it looks powdery and can blend in with the material its growing on. White mold varieties include Asperillus, Penicillium, and Cladosporium. These species were also mentioned in the green mold section; that is because the color of the mold comes from the material it is feeding on.

Yellow Mold

Yellow mold is also called slime mold because it looks like bright slime. Molds in this group include Aspergillius, Meruliporia, and Serpula lacrymans. You can find yellow mold on many surfaces, including bathrooms, food materials, tiles, walls, and wood. Healthy adults will not experience health issues when exposed to yellow mold. Children and adults with respiratory concerns and/or immune system issues may be bothered, however.