Which type of Allergic reaction is seen in patients with Allergic fungal sinusitis?

A combination of type 1 and 3 hypersensitivity reaction is thought to be involved in the pathogenesis of Allergic fungal sinusitis. It is thought to involve direct stimulation of eosinophils by a subset of helper T cells (TH2) primed by fungal antigens. It results in vigorous inflammation and polyp formation. Causative organisms includes usually those of the Dematiaceae family, but Aspergillus species are also seen. Patients usually presents with features of chronic sinusitis. Patients are treated with systemic steroids, surgery, and nasal irrigations.