[Conditions bordering on allergy].

Chronic allergic conjunctivitis constitutes a complex ocular surface disease involving many mechanisms, extending well beyond the simple field of mast cells and IgE. Lacrimal film, the eyelids, the environment, especially iatrogenic in origin, closely interact with each other and involve many cell systems such as goblet cells, eosinophils, and lymphocytes. It is therefore imperative to reach a better understanding of the mechanisms associated and eliminate confounding pathologies that may mimic allergic conjunctivitis. Dry eye syndrome or rosacea may be very close to chronic allergic diseases, and long-term use of preservative-containing eyedrops may result in inflammatory reactions that may be very difficult to discriminate from a primarily allergic disease.