Edema of any region of the larynx from a variety of causes. In the earliest stages it may be difficult to differentiate from infection, although mucosal injection and erythema are found more often in the latter. Allergic edema may result as a response from provocation induced by foods, inhalants, and drugs. The entire respiratory tract or only an isolated portion of the larynx may be affected. Laryngeal edema may also be hereditary. Other possible causes of laryngeal edema include increased capillary pressure due to superior vena cava syndrome, internal jugular vein ligation, lowered plasma osmotic failure induced by renal failure, impaired lymphatic flow, and increased capillary permeability to proteins. (From Paparella et al., Otolaryngology, 3d ed, p2253).