Sudden hearing loss occurs for various reasons and should always be dealt with immediately. In 9/10 cases, the loss is unilateral (only in one ear). Whether the change in hearing is due to wax build-up, a middle ear infection, or a sudden sensorineural decrease in hearing at multiple frequencies (inner ear), you should see your family physician or audiologist to determine the cause/type of the loss right away. It is always better to be safe than sorry. Many times, people assume it is nothing serious, only to wait too long to get medical attention and are unable to recover their hearing.
Sudden sensorineural hearing loss (SSHL) should be considered a medical emergency and be dealt with in the first 48 hours. The sooner you seek medical attention, the more likely you are to recover some or all of your hearing. Since there are more than 100 possible causes of SSHL, it is often unlikely that it will be identified. Possible treatments include antibiotics, low salt diet, and most commonly, steroids.