Inclusion Criteria:  proved diagnosis of severe, refractory eosinophilic asthma, according to GINA recommendations and International ERS/ATS guidelines; agreeing to participate this study and signing an informed consent.  Exclusion Criteria:  current smoking habit (both tobacco and e-cigarettes), concomitant diseases requiring chronic administration of immunosuppressors, biologic medications or systemic corticosteroids for any disease other than asthma History of previous or concomitant acute or chronic disease known to directly or indirectly affect eosinophil count, both in a quantitative and qualitative manner (eosinophilic lung and gastrointestinal diseases, systemic vasculitis, allergic bronchopulmonary aspergillosis, parasitic infections, etc) COPD/Asthma overlap. Inability or denial to sign the informed consent.