Introduction: Papular urticaria caused by the bites of fleas traditionally has been defined as a chronic allergic disease. However, currently no clear relationship has been described between this pathology and common allergic diseases.Objective: The expression of IL-10, IL-4 and IFN-γ as markers of effector T cell responses was examined in skin lesions of patients with papular urticaria by flea bite.Materials and methods: Fourteen skin lesion biopsies were sampled from children with a clinical diagnosis of papular urticaria by flea bite and were compared with 5 healthy skin biopsies of children with no history of the disease. All children were under 12 years old. RNA was extracted with trizol and the expression levels of cytokines were analyzed by real time PCR technique.Results: A wide range in the expression levels of IFN-γ and IL-10 was noted as well as constant low values of IL-4. Three distinct profiles were observed, but which did not correspond to a recognizable pattern among the patients. The samples obtained from healthy tissues showed no expression of any of the cytokines.Conclusions: This is the first characterization of cytokines that mediate the immune response at the site of the skin lesion in children with papular urticaria by flea bite. The data indicated that the local response was mixed and that a single phenotype is not predominant among the patients.