The conjunctiva (from conjugere: to gather) is one of the elements of the protective apparatus of the eyeball with the eyelids and the lacrimal apparatus. It is a translucent membrane that lines the inner surface of the eyelids and covers the sclera. It is covered by two layers of stratified, non-keratinized conjunctival epithelial cells (ConEpiC). The ConEpiC can be distinguished from the corneal epithelium by a specific keratin expression profile. ConEpiC is covered by a mucin-rich glycocalyx, which promotes tear adhesion, prevents pathogen penetration and provides lubrication. Decreased or lost mucin/glycocalyx production results in squamous metaplasia, which can lead to dry eye and ocular surface disease. ConEpiCs also respond to histamine by stimulating phosphatidylinositol turnover and secreting cytokines. Therefore, they could be a good target for the development of topical ocular drugs to treat allergic conjunctivitis.