When the hearing goes, it does not - luckily - have to be permanent. Blocked ears, sinuses or fever reducing medicine can also be the cause.

Most people experience reduced hearing or tinnitus during their lives. For many the condition is permanent, but in many cases their hearing can often return to normal again.
Here is a guide to the three most common causes of temporary reduced hearing – and how the symptoms can be beaten.

Blocked ears 
 
Ear wax can block the ears and thereby reduce the ability to hear until the wax is removed. Blocked ears can also lead to dizziness and pain.
People with blocked ears should not attempt to remove the wax themselves with a cotton swab. That can just make matters worse. Instead, he or she should consult a doctor. The doctor will typically remove the wax with a something that can dissolve it, either through flushing the ear or manually.
 
Blocked sinuses 
 
Blocked sinuses as a result of a cold, sinus infection or allergies can result in temporary hearing loss. The blocked sinuses cause the Eustachian tube, which regulates the pressure within the inner ear, to swell up, so that the connection between the middle ear and throat is closed off.
If this condition continues for more than 10 days and/or if it occurs more than three times a year, this could suggest an undiagnosed allergy. The patient’s doctor should then conduct an allergy evaluation.
 
Fever reducing medicine

High doses of aspirin, ibuprofen and other so-called non-steriod anti-inflammatory preparations can cause tinnitus.
A humming or ringing feeling in the ear can occur, if a person ingests either 10 aspirin or 800 milligrams of ibuprofen a day.

Kilde: www.star-telegram.com