Growth and Distribution

Ascospores refers to spores produced in a sac-like structure known as an ascus (plural asci). These spores are specific to fungi of the phylum Ascomycota.  Ascomycota is a broad division containing a large number of genera and individual species.  Identification of the genus and/or species based on spore morphology alone is not always possible, therefore these spores are often given the more general classification of “Ascospores” in microscopic analysis.

Ascospores are found worldwide with prevalence and distribution depending on particular genus and species.

Outdoors: Ascospores are found ubiquitously in outdoor environments; often found on dead and decaying plant material.  Many types are known to have pathogenic or parasitic properties in plants.

Indoors: Common substrates include damp building materials such as gypsum or lumber, carpeting, dust, and other organic materials.

Health Effects


Ascospores can be allergenic to sensitive individuals, most often producing Type I or Type III hypersensitivity reactions. These include allergic asthma, conjunctivitis (redness of the eye), rhinitis (hay fever), anaphylaxis, angioedema (dermal swelling), urticarial (hives) or hypersensitivity pneumonitis (Type III). (5)

Reactions due to spore inhalation may increase following rain or high humidity. (5)

Unlike some fungi which rely on air currents for spore dispersal, ascomycetes are capable of a more active form of spore dispersal that utilizes water droplets to catapult their spores into the air. Various species of Ascospores are known to use this method to liberate spores every single day, regardless of air flow.  Subsequently, exposure to ascospores may be more consistent from day to day than exposure to other spores which are only dispersed with adequate air currents. For this reason these spores may be of particular interest in cases of chronic respiratory disease such as asthma and rhinitis (5).


Some types can be pathogenic; dependent upon genus and species.


Vary greatly depending on genus and species.


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