BACKGROUNDFungal spores are the predominant biological particulate in the atmosphere of Puerto Rico, yet their potential as allergens has not been studied in subjects with respiratory allergies. The purpose of this study was to determine the level of sensitization of subjects with respiratory allergies to these particles.METHODSSerum samples were drawn from 33 subjects with asthma, allergic rhinitis, or nonallergic rhinitis and 2 controls with different skin prick test reactivity. An MK-3 sampler was used to collect air samples and the reactivity of the sera to fungal particles was detected with a halogen immunoassay.RESULTSAll subjects reacted to at least 1 fungal particle. Thirty-one subjects reacted to ascospores, 29 to basidiospores, 19 to hyphae/fungal fragments, and 12 to mitospores. The median percentage of haloes in allergic rhinitis subjects was 4.82% while asthma or nonallergic rhinitis subjects had values of 1.09 and 0.39%, respectively. Subjects with skin prick tests positive to 3, 2, 1, or no extract had 5.24, 1.09, 1.61, and, 0.57% of haloed particles, respectively. If skin prick tests were positive to basidiomycetes, pollen, animals, or deuteromycetes, the percentages of haloes were 4.72, 4.15, 3.63, and 3.31%, respectively. Of all haloed particles, 46% were unidentified, 25% ascospores, 20% basidiospores, 7% hyphae/fungal fragments, and 2% mitospores. IgE levels and the number of positive skin prick test extracts correlated with the percentage of haloes.CONCLUSIONIn tropical environments, sensitization to airborne basidiomycetes, ascomycetes, and fungal fragments seems to be more prevalent than sensitization to mitospores in subjects with active allergies, suggesting a possible role in exacerbations of respiratory allergies.