Histologic studies of guinea pig skin: Different stages of allergic reactivity to flea bites

Abstract

A definite sequence of skin reactions occurs when guinea pigs are exposed to flea bites. The sequence is composed of stages that are observed at the bite sites and can be classified in terms of allergic phenomena. This study presents a sequential morphologic analysis of these allergic stages in terms of histopathologic events. When the different types of skin sensitivity in guinea pigs were defined both by macroscopic and microscopic characteristics, the following stages were noted: 1.I. Induction stage, during which no abnormal macroscopic or microscopic changes occurred in the skin;2.II. Stage of delayed skin reactions only, characterized by intense mononuclear infiltration at the vicinity of the bite site some 24 hours following the bite;3.III. Stage of immediate and delayed reactions, immediate reactions appearing 20 minutes after the bite and characterized by an eosinophilic infiltration; the delayed reaction appearing within 24 hours, characterized by mononuclear infiltration;4.IV. Stage of immediate reactivity only, the reaction appearing 20 minutes after the bite and characterized by an infiltration of eosinophils at the bite site;5.V. Stage of nonreactivity resulting from desensitization, wherein no skin reactivity was observable and no cellular abnormalities occurred.