Purpose: The effect of ocular artificial teardrop containing benzalkonium chloride (BAC) on nasal mucosa was investigated.Materials and methods: There were two different treatment trial groups. Each dry eye syndrome (DES) patient received the ocular lubricant treatment four times a day in both groups (one group containing BAC, the other group was not). Moistened sterile cotton-tipped applicators were placed in both nostrils and were immediately cultured prior to ocular lubricant treatment and at the end of treatment trial. The bacterial culture-positivity rate, species of bacteria, and drug sensitivity were recorded in the two groups during pre-treatment and post-treatment.Results: There were 20 patients in each group with a mean age of 53.14 years (36 female, 4 male). At the beginning of the treatment trial, Staphylococcus epidermidis was the most frequently isolated organism from the nasal cavity accounting in 24/40 patients (60%). Of the 40 organisms isolated from the nares prior to treatment trial, 37 (92.5%) were sensitive to gentamycin. At the end of 1 month of treatment trial in patients who were treated with ocular lubricants containing BAC, none of the nasal cultures showed growth of any organisms. However, patients who were treated with ocular lubricants not containing BAC demonstrated persistent positive nasal cultures with the same species and the same antibiotic susceptibility profile at the end of the treatment trial period.Conclusion: Topically applied ocular lubricants including BAC has an anti-bacterial activity on nasal flora in DES patients.