PTX3 behaves as an acute-phase response protein as its blood levels rapidly and dramatically increase during endotoxic shock, sepsis, and other inflammatory and infectious conditions. Therefore, this study was designed to investigate a possible role of PTX3 in children with Atopic Dermatitis (AD). One-hundred-and-thirty-six patients (37 females, 99 males, mean age 10.4 years) were enrolled in the study. One hundred patients (74%) had only respiratory symptoms (allergic rhinitis and/or bronchial asthma); thirty-six patients (26%) showed dermatitis associated with respiratory allergy (allergic rhinitis and/or bronchial asthma). PTX3 levels were higher in children with AD and there was a significant correlation between serum PTX3 levels and SCORAD index (p-value=0.0001, rho=0.658). Therefore, this study may show that PTX3 might be a reliable marker for the severity of AD in children with respiratory allergy.