Benzalkonium Chloride - Safety

Safety

ADBAC is highly toxic to fish (LC₅₀ = 280 μg ai/L), very highly toxic to aquatic invertebrates (LC₅₀ = 5.9 μg ai/L), moderately toxic to birds (LD₅₀ = 136 mg/kg-bw), and slightly toxic to mammals (LD₅₀ = 430 mg/kg-bw). Benzalkonium chloride solutions of 10% or more are toxic to humans, causing irritation to the skin and mucosa, and death if taken internally.

Several studies have identified allergic reactions to benzalkonium chloride by some individuals but several studies have cast doubt on its reputation for other negative health effects. It is still widely used in eyewashes, nasal sprays, hand and face washes, mouthwashes, spermicidal creams, and in various other cleaners, sanitizers, and disinfectants. Manufacturers of over-the-counter artificial tears and eye washes became concerned about chemical sensitivity from long-term daily use and have in some products substituted EDTA as a preservative. Some have packaged eye drops in single-use vials with no preservative for sensitive eyes. There has also been concern that long-term use of benzalkonium as a preservative in nasal sprays may cause swelling of mucosa and lead to rhinitis medicamentosa. Although some studies have found no correlation between use of benzalkonium chloride in nasal sprays and rhinitis medicamentosa, others have found benzalkonium chloride in oxymetazoline nasal spray to worsen rhinitis medicamentosa in healthy volunteers after both long-term use and short-term use.

Contact lens solutions typically contain 0.002% to 0.01% benzalkonium chloride. K. C. Swan found that repeated use of benzalkonium chloride at concentrations of 1:5000 (0.02%) or stronger can denature corneal protein and cause irreversible damage to the eye. Swan also found that 0.04% to 0.05% solutions of benzalkonium chloride can cause punctures of the corneal epithelium. The disadvantages of using benzalkonium chloride solutions with contact lenses are also discussed in the literature.

A disinfectant containing benzalkonium chloride and the related compound didecyldimethylammonium chloride (DDAC) has been identified as the most probable cause of birth defects and fertility problems in caged mice.

A 2009 study has found that benzalkonium chloride, when used in less than lethal concentrations, resulted in an increased resistance to the disinfectant solution, and a 256-fold increase in resistance of the bacteria Pseudomonas aeruginosa to the ciprofloxacin antibiotic, even though the bacterial colonies had not been previously exposed to the antibiotic.

A 2012 study reported that simultaneous ocular exposure to an inert antigen and benzalkonium chloride leads to a significant change in the systemic immune response to the administered antigen in mice, thus suggesting that the preservative's effects could be more profound than the local disruption of the epithelial barrier integrity.