Although chronic sinusitis widely affects the adult population, the treatments currently used did not always satisfactorily solve the symptoms. Traditional therapy with steroids and antibiotics presents risks and benefits and the new drugs, i.e., monoclonal antibody, are valid solutions despite being quite expensive. Natural molecules could be a valid treatment that combines good efficacy and low price. We conducted a case -control study to evaluate the benefit of an oral supplement with Ribes nigrum, Boswellia serrata, Bromelain and Vitamin D on chronic sinusitis symptoms. 60 patients were randomly assigned to one of the three groups: control using nasal steroids only, treatment 1 using nasal steroid and 1 dose of the oral supplement for 30 days and treatment 2 in which patients used nasal steroid and two oral supplement doses daily for 15 days. Conditions of the nasal mucosa and a blood sample (WBC, IgE and CRP) were analyzed at T0, T1 (15 days after treatment) and T2 (30 days after treatment. Patients treated with the supplement improved their nasal findings (hyperemia of mucosa and rhinorrhea) with statistically significant differences from the control. Our preliminary data suggest that the addition of supplement containing Ribes nigrum, Boswellia serrata, Vitamin D and Bromelain to the traditional local therapy (nasal spray with cortisone) can be a supporting therapy to modulate the local inflammation in the nose in patients affected by chronic sinusitis.