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Featured Mold – Aspergillus and Penicillium

Aspergillus and Penicillium are two of the most common mold genera that we see in air samples.  When dealing with spore trap lab results, you will often see these types listed together in groups such as Aspergillus/Penicillium, Asp/Pen, or Pen/Asp. Visually, spores of these genera are so similar that analysts can not differentiate them, so they are reported together. Occasionally spores from other genera that produce similar small amerospores (spores with no septations and no projections longer than the length of the spore) will be counted in this group also. Because there are over 200 separate species of both Aspergillus and Penicillium, an Asp/Pen designation on a lab report represents a large grouping of different species.

microscopic photo of aspergillus
Aspergillus conidia at 400x

Since there are so many different species in this group, we can find Aspergillus and Penicillium in a broad range of habitats. Some species such as Aspergillus penicillioides are xerophilic, which means they grow with only a small amount of moisture. Other species like Aspergillus versicolor are more prevalent in environments with high water activity. In a home without any moisture problems you can often find Aspergillus and Penicillium growing on spoiled fruit.

Like all mold, Asp/Pen can cause allergic reactions in people who are sensitive to these types. They can also occasionally cause fungal infections of the ear, eyes, and skin.  In people with underlying health issues and compromised immune systems, Aspergillus can infect the lungs causing pulmonary aspergillosis.

Surprisingly, mold isn’t always the bad guy. There are many important uses for fungi in industry. For example, Aspergillus and Penicillium are used to make all sorts of products from cheese to pharmaceuticals. Without these fungi we would be without many important antibiotics, soy sauce, or soft drinks.

Dylan McIntosh

Dylan McIntosh

Dylan McIntosh is a Senior Project Manager that performs indoor air quality assessments, industrial hygiene testing, and laboratory mold analysis. Mr. McIntosh holds a Bachelors of Science degree in Biology from the University of Illinois - Springfield. Dylan is a Certified Industrial Hygienist (CIH) and an Pan American Aerobiology Certification Board (PAACB) Certified Spore Analyst. In his words… “Throughout my life, I always had a dream of becoming an astronaut. That dream hasn’t worked out (yet) so I started a career in the next best thing, indoor air quality! In my free time I enjoy outdoor activities with my dog, cooking, and being involved with A Special Wish - Chicago; a local charity.”

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19 thoughts on “Featured Mold – Aspergillus and Penicillium

    Hi I’m currently having my apartment redone because air conditioning,was going bad released water behind the wall and went on carpet they left it therefor a month but the first time it was a year and left on floor I did the samples and took to labAspergillosis penicillium I have 3autoimmune disorders since there was the damage a year ago I’ve had pneumonia with sepsis 3 times and since they never cleaned the mold safely every time I go there I’m sick with throat and breathing problems

    The crawl space under our house has been diagnosed as containing ASP-Pen, according to the tech the elevation is quite high. We need to clean out about 10 yards of junk ,I am wondering what the exposure might cause while removing it.

    Hi there,
    So are aspergillus and penicillin related, or do they just bear resemblance to each other? Trying to understand this from a possible allergy standpoint. If someone is allergic to one, what is the likelihood of them being allergic to the other?

    They are grouped together on air sampling reports because visually, the spores are almost impossible to reliably differentiate. Taxonomically they are as related to each other as humans are to gorillas. Allergies are very individualized, some people are allergic to both, others are allergic to just one, and some are only allergic to specific species. The only way to know would be to have a detailed mold allergen test done by a doctor.

    Recently had an a/c unit (not central air) with a clogged condensate line causing water to accumulate within the unit. Not certain how long this went unnoticed but was likely a matter of 4 to 6 months. The unit has been removed and replaced. Air quality testing shows aspergillius/penicillium. Does This this require full remediation . I do seem to have an allergy related to this.

    Count per m/3 – 121 – 25%

    Aspergillus and Penicillium are made up of hundreds of different species, each with their own specific preferred growth conditions. I do not know of any specific species that can grow on almonds, but I can only assume it is possible.

    What is your favorite method of remediation for Penicillium/Aspergillus in the wall cavity of a home?
    I’m desperately seeking truth as I have autoimmune disorders and can’t be exposed to the mold. Yet, we’d have to sell our home after the costs of traditional remediation.
    We are being directed by our inspector to local company that uses a dry fogging product called InstaPURE (a Sterilant) then followed EverPURE. It’s the second dry fog application in the two-step process that supposedly prevents the mold from returning. The company markets it as the only fogging BioStat of its kind to be approved by the EPA for mold remediation.
    Any information you can share would be deeply appreciated.


    Fogging is not a proper way to remediate any types of mold. The goal for remediation is the physical removal of mold from the building materials. Fogging may kill mold, but it does not magically make it disappear. Even dead mold can cause allergic reactions in susceptible people, so the mold needs to be physically removed from the space.

    I just had air tested in condo and it was positive for Aspergillis/penicillin like mold at 8,800 count.
    There are dome black spots on popcorn ceiling in one area…not much.
    Should I be concerned?
    Am I In danger?

    We are not medical professionals so we are not qualified to say if your health is at risk.

    With the info you have provided there is not much I can say, it is the industry standard to compare air samples to an outdoor air sample taken at the same time.

    Can you comment on an air test that does have outdoor vs indoor spore count? Trying to get information on levels.

    We are in a rental, have lived here for 5 years. During this time multiple water leaks from roof issues, internal plumbing from upstairs bathroom down walls in 1st floor entry way which required repair. Never convinced repairs got everything, had a test done and came back with the following elevated levels:

    Control Front: 5/200/3.1%
    Control Back: 2/80/1.1%
    Master Bedroom: 18/760/35.5%
    2nd Bedroom: 30/1300/37.9%
    Living Room: 32/1400/32.6%

    Control Front: 23/970/15%
    Control Back: 16/680/9.1%
    Master Bedroom: 16/680/31.8%
    2nd Bedroom: 10/420/12.2%
    Living Room: 36/1500/34.9%

    Control Front: none
    Control Back: none
    Master Bedroom: 1/40/0.9%
    2nd Bedroom: none
    Living Room: none

    Immediate Question: Are the levels of Asp/Pen safe to be in the home?