Indoor and Outdoor Fungal Allergens and Impacts on Respiratory Allergic Disease

Abstract

Humans have a historic and intimate relationship with fungi. Fungi cause decay in the environment and a variety of human disease states including respiratory disease. Immunocompromised persons are particularly susceptible to fungal infection; however, the greater impact of fungi in general is through allergic mechanisms. This impact has been extensively documented in epidemiologic studies. Typically, fungal spore exposure has been examined in the outdoor environment; however, in recent decades, lifestyle changes have resulted in increased concern about fungi in the indoor environment. This review examines evidence for the relationship between fungal exposure and respiratory disease as indicated by documented physician interactions comparing times of high spore exposure with times of low exposure. The taxa Alternaria has been especially associated with respiratory difficulties, but there is extensive cross-reactivity among fungal allergens. We examine recent evidence that damp housing and associated indoor fungal load relate to respiratory disease and some possible mechanisms by which fungal products might cause sensitivity. We also offer some steps allergists might suggest to their patients that may help alleviate fungal exposure.