Tinnitus is not itself a disease but a symptom resulting from a range of underlying causes. Tinnitus is the ability to perceive sounds which are always present within the auditory (hearing) system. This is a failure of the compensatory mechanisms that are part of its normal function. This "phantom" sound can create distress in the sufferer. Causes include ear infections, foreign objects or wax in the ear, nose allergies that prevent (or induce) fluid drain and cause wax build-up, and injury from loud noises. Tinnitus is also a side-effect of some oral medications, such as aspirin, and may also result from an abnormally low level of serotonin activity.