Common cold. Artwork of a sagittal (side view) section through a human head and neck to show some features of the common cold. The common cold is a viral infection causing fluid discharge (yellow) from inflamed mucous membranes. Inflammation of the mucous membranes of the nose (rhinitis) and the sinuses (sinusitis) are common symptoms. Two sinuses (membrane-lined hollows inside the facial bones) are shown here: one in the forehead and one behind the nose. Mucus is also seen going down the trachea to the lungs. Inflammation of the throat is pharyngitis. Middle ear inflammation (otitis media), by the cochlea (pink, upper right), comes through the eustachian tube from the throat.