Most Common Molds

According to the Centers for Disease Control (CDC), the most common molds found inside homes and buildings are Cladosporium, Penicillium, Aspergillus, and Alternaria. Below is a brief discussion of each.


Cladosporium commonly exists in the outdoor and indoor environment. Illness through exposure to Cladosporium is very rare, but has been known to cause infections, including skin, eye, and sinus infections. Fungal Meningitis is a more severe illness from exposure to Cladosporium. There has been an outbreak of fungal meningitis in several states recently, but this was associated with contaminated medical steroid injections, not from common exposure in homes and buildings.


Penicillium is one of the most common types of mold in indoor environments. It thrives on organic material such as food and soil particles (think of moldy bread or fruit). Unless you eat it, exposure to Penicillium carries the same health hazards as most molds, including skin, eye, or respiratory irritation. Ingesting it, however, can cause serious illness. Those with hypersensitivity or a compromised immune system may also experience more severe reactions just by exposure to airborne Penicillium.


Aspergillus is also a very common type of mold and exists in any oxygen-rich environments, and can typically be seen growing on starchy foods and outdoors on trees and plants. To healthy humans, moderate exposure typically does not have serious consequences, other than maybe some allergic reactions or irritations. Those with compromised immune systems, especially those with chronic lung diseases, can experience severe health problems from exposure to Apergillus.


Alternaria is a common allergen, and usually produces mild symptoms such as skin or eye irritation, or ” hay fever”. It can cause asthma, and like other mold types, can cause more serious problems in those with compromised immune systems. Alternaria is usually green, black, or gray in color. It is known to cause spoilage in plants used for food and, like other mold types, is very common in the outdoor environment and typically does not cause problems to humans in the outdoors.

*It may be dangerous and hazardous to your health to attempt household removal on your own. The content of this website is provided for general informational purposes only and is not intended as, nor should it be considered a substitute for, professional mold removal advice. To learn more, please read our Terms of Use.

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