Benzalkonium chloride (BAC) is a quaternary ammonium compound commonly employed as a preservative in several multidose eye drops. Its use is associated with several adverse events, particularly when used chronically. Topically instilled BAC acts not only on superficial structures but also reaches deeper tissues (trabecular meshwork, optic nerve) and can be deleterious in patient under chronic treatment. In glaucomatous patients, BAC is the primary cause of ocular surface disease (OSD), and it can lead to significant morbidity, influence treatment compliance, quality of life, and surgical outcomes. Clinical and experimental evidence demonstrates that BAC causes instability of the tear layer, loss of goblet cells, apoptosis, subclinical neuroinflammation, and antibiotic resistance. Considering the validity of the alternative formulations (alternative preservatives or preservative-free formulations) it is unreasonable to persist in using such toxic compounds and, perhaps it is time for a moratorium on the use of BAC in eye drops.