<b>Background and aim</b>: Costa Rica is a tropical country in which a high concentration of aerial basidiospores has been found, which measure between 4-13 µm and are capable of arriving to the lower respiratory system, surpassing the nasal barrier. This study aims to find possible sources of environmental contamination by basidiomycetes and to determine if it is necessary to routinely analyze this allergen in the Costa Rican population that suffer from rhino bronchial allergy. <b>Methods</b>: The percentage of patients allergic to the extracts of basidiomycetes, specifically smuts like <i>Sporisorium cruentum</i> and <i>Ustilago cynodontis </i>and rusts <i>Puccinia graminis </i>subsp. <i>graminis </i>was determined. Also, we collected panicles of <i>Panicum maximum</i> to assess their contamination by basidiomycetes. <b>Results:</b> We found that 59.23% of patients were allergic to mushrooms and that the fungi type for which more patients had allergy is the basidiomicetes. At the same time, a 100% of the collected panicles were contaminated with a fungus of the genus <i>Ustilago.</i> <b>Conclusion:</b> Most of the patients studied were allergic to basidiomycetes, therefore, we strongly recommend that Costa Rican allergists constantly test for these extracts

Basidiomycetes; allergy; fungi; <i>Ustilago</i>