When sections of the ear behind the eardrum, or the "middle year" is affected with bacterial or viral infection, ear infection is caused. These infections can be painful due to fluid building up in the ear, and inflammation. The ear infections can be chronic or acute in nature. Acute ear infections are the ones which causes pain, but have a short duration. Chronic infections do not clear up or recur many times. Such chronic ear infections can cause permanent damage to middle and inner ear and cause hearing loss.
Ear infections occur when eustachian tubes become swollen or blocked, resulting in fluid build up in middle year. Eustachian tubes run from each ear directly to the back of the throat, and are small in size. The blockage of eustachian tube can be due to allergies, cold, sinus infections, excess mucus, smoking, infected adenoids or change in air pressure.
Ear infections occur most commonly in young children as they have short and narrow eustachian tubes. Other factors that increase risk of ear infection are altitude changes, climate changes, exposure to cigarette smoke, pacifier use and recent illness.