Reaction types & epidemiology
Saliva proteins injected by hematophagous insects during the blood meal regularly induce a humoral and cellular immune response in the host frequently leading to cutaneous adverse reactions. Two main reaction patterns are commonly found in humans and in animals: (1) a short-lived immediate reaction with wheal formation, erythema, and itch occurring within 15 minutes. (2) a delayed skin reaction consisting of an indurated itchy papule of up to 10 mm in size peaking around 24 h after the bite and persisting for days.
There is evidence that the cutaneous immediate reaction represents an IgE-mediated type 1 response while the delayed papule is primarily T-cell mediated.81,82 Both reaction patterns are ubiquitous within the general population with up to 90% showing immediate skin reactions after mosquito bites, and up to 70% delayed reactions.81,83-86
Epidemiological data suggest that hosts pass through different stages of hypersensitivity until acquiring secondary tolerance.