Cyanobacteria: An unrecognized ubiquitous sensitizing allergen?

This study was designed to investigate the prevalence of skin sensitization using detoxified cyanobacterial reagents in a chronic rhinitis population. Subjects ≥6 years of age who presented for allergy consultation to a community allergy practice and required skin-prick testing (SPT) to common seasonal and perennial aeroallergens were enrolled after signing an informed consent. Detoxified cyanobacteria species were used for skin testing. Skin testing of unexposed, nonsensitized control subjects using these detoxified cyanobacterial skin test reagents was performed to identify irritant threshold responses. All subjects signed an Institutional Review Board‐approved informed consent before participation. Two hundred fifty-nine patients ranging in age between 7 and 78 years old underwent testing. The majority were white female patients and over two-thirds (73.4%) were atopic. Seventy-four (28.6% of the population) patients were SPT⁺ to at least one of the cyanobacteria species. Positive SPTs were present in 86% of patients to Microcystis aeruginosa and 12% of patients to Aphanizomenon-flos aquae. There was a strong association between severity of atopy (number of positive SPTs), having allergic rhinitis and sensitization to one or more cyanobacteria species (p < 0.001). This is the first study to show that cyanobacterial allergenicity resides in nontoxin-containing components of this organism.