In addition to being a drainage system, the lacrimal ducts actively defend the eye through the action of the lacrimal pump, the presence of resident flora (lacriome) and the mucosa-associated immune tissue. Infection occurs when mucosal immune functions are overwhelmed. Lacrimal infection is a vicious circle, in which infection leads to inflammation and post-inflammatory sequelae, themselves a source of occlusion and stagnation, which in turn encourages infection. Whatever the initial trigger - post-traumatic occlusion, inflammation (e.g. allergic) or infestation by a virulent germ, the management of lacrimal duct infection must take account of this vicious circle. When infection sets in, changes in the mucosa can range from submucosal inflammatory infiltrates to pseudocysts, and in the most severe cases to metaplasia, dysplasia and squamous cell carcinoma. Histological sampling is therefore imperative in the case of surgery on a chronically infected mucosa. Clinical assessment, aided if necessary by a dacryoscan, must be able to detect differential diagnoses (lacrimal sac carcinoma, dacryocystocele in children) and serious forms (gonococcal ophthalmia neonatorum, peridacryocystitis), look for signs of dacryoliths, and differentiate between acute and chronic infection. Antibiotic treatment should be adapted to the identified or presumed organism involved or used sparingly in cases of chronic infection. Dacryoliths can be removed by curettage in the case of canaliculitis with concretions, but surgery is required for larger dacryoliths (canaliculotomy, or dacryocystorhinostomy in the case of lacrimal sac dacryoliths). Antibiotic prophylaxis for lacrimal surgery is recommended only in cases with associated rhinosinusitis, inflammation of the lacrimal sac, or a history of infected mucocele or dacryocystitis.