In the maritime environment, characterized by a great biodiversity, employees can be during their work exposed to chemical and above all biological substances. Some of them are the cause of occupational asthma. This is the case for some fished products such as crustaceans and mollusks and also for some products carried as cargo like cereals or chemicals used in the maintenance of ships. This article is a review of known etiological factors of occupational asthma (OA) to which seafarers and other maritime workers are likely to be exposed.