Ocular hypersensitivity reactions to ophthalmic preservatives are:
- IgE-mast cell mediated
- cell mediated
- irritant (toxic)
Quaternary ammoniums (benzalkonium chloride) are most commonly associated with irritant toxic reactions (8% of cases).
Organomercurials (thimerosal) and alcohols (chlorobutanol) have the highest association with allergic responses.
Allergy to ophthalmic preservatives. Hong, Jison; Bielory, Leonard. Current Opinion in Allergy and Clinical Immunology: October 2009 - Volume 9 - Issue 5 - p 447-453.
Image source: Benzalkonium chloride, Wikipedia, public domain.