Your healthcare provider will ask about symptoms and medical history, and perform a physical exam. When there is ear pain or drainage from the ear, then infection is likely to be present. If the child is too young to report pain, the doctor or nurse practitioner must rely solely on looking into the child's ear with a lighted instrument, called an otoscope. The eardrum may be red, have pus behind the eardrum, and bulge outward because the fluid behind it is under pressure. A small tube and bulb (insufflator) may be attached to the otoscope so that a light puff of air can be blown into the ear. This helps your healthcare provider see if the eardrum is moving normally. When infection is present the eardrum is often stiffened by the presence of fluid behind it and does not move. A red, bulging drum that does not move with an air puff is a very good sign that acute otitis is present.

Unfortunately, it is often very difficult to see the eardrum in very young children, and ear wax frequently makes getting a good view of the drum next to impossible. Worse, even in the absence of wax, the accurate diagnosis of middle ear infection using an otoscope is not easy. Most studies suggest that even experienced doctors may overdiagnose acute ear infections, especially if an air puff insufflator is not used. Doctors may have a particularly difficult time distinguishing between children with chronic otitis (who frequently do not need antibiotics) and those with acute otitis (for whom antibiotics are often helpful). The use of a microscope to examine the ear may also help.

Other tests may also be performed, especially if you or your child have had repeated ear infections. Tests may include:

Tympanometry—A soft plug is inserted into the opening of the ear canal. The plug contains a speaker, a microphone, and a device that is able to alter the air pressure in the ear canal. This allows several different measures of the middle ear and eardrum and provides important information about the condition of the ear, but it is not a hearing test.

Hearing Test—A hearing test may be ordered if you or your child have had repeated ear infections or are showing signs of hearing impairment, such as speaking in a louder voice, sitting closer to the television or turning up the volume.

Tympanocentesis—A needle is used to withdraw fluid or pus from the middle ear under local or general anesthesia. This fluid can then be cultured to determine if bacteria are present in the fluid. Once the bacteria are cultured, the lab can determine which drugs are best for treatment. However, the fluid does not always have bacteria in it.