Allergic disorders are typically characterized by an inflammatory response to allergen exposure. PTX3 behaves as an acute-phase response protein as there is a relationship between PTX3 plasma levels and disease severity. Therefore, this study was designed to investigate a possible role of PTX3 in children with allergic rhinitis. One hundred patients (28 females, 72 males, median age 11 years) were enrolled in the study. All patients were monosensitized: 43 (43%) to seasonal allergens (Graminaceae), 57 (57%) to perennial allergens (house dust mites, cat and dog epithelium, alternaria tenuis). Patients' blood samples for assessing serum PTX3 levels were performed during the spring. Children with rhinitis had higher PTX3 levels and there was a significant relationship between symptom severity and serum levels. Therefore, this study shows that PTX3 serum levels could be a reliable marker for symptom severity in children with allergic rhinitis.