Background Although basidiospores are a major component of the air spora in many parts of the world, their clinical significance as triggers of respiratory allergy has rarely been demonstrated. Therefore, the class of basidiomycetes as an aeroallergen is not well known. Objective To demonstrate a cause and effect relationship between respiratory allergy and basidiospores, we illustrate this case report of a 38-year-old housewife. Methods Skin prick test, immunoblot, and active anterior rhinomanometry were used as diagnostic tools to verify specific reactivity of a Pleurotus pulmonalis spore extract. Two atopic subjects served as controls. Results The skin prick test positive study subject reacted with subjective and objective signs including a significant drop of the FEV1 by nasal challenge at a concentration of 0.1 mg/mL of the Pleurotus spore extract while both controls were negative even at a higher test concentration. IgE-immunoblot revealed several distinct bands in the serum of the Pleurotus-sensitized subject. Conclusion Spores of Pleurotus pulmonalis, a common mushroom of the fungal class of basidiomycetes, can cause specific, IgE-mediated acute rhinoconjuncivitis and asthma in sensitized individuals.