Hissing cockroaches are popular, but they also host potent mold allergens

Some people are allergic to the species of cockroaches that are household pests. In those cases, the bugs’ actual bodies contain allergens. In the case of the Madagascar hissing cockroaches, the most potent mold allergens live on and around the insects instead.

Benoit and colleagues examined the insects from an Ohio State-based colony as well as those found in home collections, zoos, pet stores and science classrooms across Ohio.

The research group tested the feces first, and, as expected, found mold in the bugs’ waste. Then the team examined the giant cockroaches themselves, both outside and inside their bodies, to see what other allergens might be present.

The most commonly found mold species found on the body surfaces of young and adult Madagascar hissing cockroaches were Rhizopus, Penicillium, Mucor, Trichoderma and Alternaria, several of which are listed by the Centers for Disease Control and Prevention (CDC) as common indoor molds. Colonies of the mold species Aspergillus niger, a common contaminant of food, were particularly plentiful in the feces and external shells that had been discarded as the insects molted.

Few molds were found inside the cockroaches’ bodies.

Molds are fungi that grow best in humid conditions, and spread and reproduce by making spores. Benoit said all of the mold species found on and around the hissing cockroaches are capable of producing huge quantities of spores. And the spores themselves can get on bug handlers’ skin or be inhaled, triggering allergic responses in those sensitive to the molds.

For people who are allergic to molds, exposure can cause symptoms such as nasal stuffiness, itchy or burning eyes, wheezing or skin irritation, according to the CDC. Some people with serious allergies to molds may have more severe reactions.

Benoit now is pursuing additional studies on one surprise among the findings: Symbiotic mites also live on the cockroaches, and help keep them clean.

“The mites sweep the surface and remove old food particles and debris, so they remove places on which fungi can grow,” Benoit said.

Benoit conducted the project with Jay Yoder and Brian Glenn of Wittenberg University and Lawrence Zettler of Illinois College.

Contact: Joshua Benoit, (614) 247-5093;
Written by Emily Caldwell, (614) 292-8310;