Pain is the predominant complaint and the only symptom directly related to the severity of acute external otitis. Unlike other forms of ear infections, the pain of acute external otitis is worsened when the outer ear is touched or pulled gently. Pushing the tragus, the tablike portion of the auricle that projects out just in front of the ear canal opening, so typically causes pain in this condition as to be diagnostic of external otitis on physical examination. Patients may also experience ear discharge and itchiness. When enough swelling and discharge in the ear canal is present to block the opening, external otitis may cause temporary conductive hearing loss.

Due to the fact that the ear and throat are often interconnected, irritation (whether it be in inflammation or a scratching sensation) is normal. However, excessive throat symptoms may likely point to the throat as the cause of the pain in the ear rather than the other way around.

Because the symptoms of external otitis lead many people to attempt to clean out the ear canal (or scratch it) with slim implements, self-cleaning attempts generally lead to additional trauma of the injured skin, so rapid worsening of the condition often occurs.

Swimming in polluted water is a common way to contract swimmer's ear, but it is also possible to contract swimmer's ear from water trapped in the ear canal after a shower, especially in a humid climate.^[2] Constriction of the ear canal from bone growth (Surfer's ear) can trap debris leading to infection.^[3] Saturation divers have reported Otitis externa during occupational exposure.^[4][5][6] Even without exposure to water, the use of objects such as cotton swabs or other small objects to clear the ear canal is enough to cause breaks in the skin, and allow the condition to develop.^[7] Once the skin of the ear canal is inflamed, external otitis can be drastically enhanced by either scratching the ear canal with an object, or by allowing water to remain in the ear canal for any prolonged length of time.

The two factors that are required for external otitis to develop are (1) the presence of germs that can infect the skin and (2) impairments in the integrity of the skin of the ear canal that allow infection to occur. If the skin is healthy and uninjured, only exposure to a high concentration of pathogens, such as submersion in a pond contaminated by sewage, is likely to set off an episode. However, if there are chronic skin conditions that affect the ear canal skin, such as atopic dermatitis, seborrheic dermatitis, psoriasis or abnormalities of keratin production, or if there has been a break in the skin from trauma, even the normal bacteria found in the ear canal may cause infection and full-blown symptoms of external otitis.^[8]

Fungal ear canal infections, also known as otomycosis, range from inconsequential to extremely severe. Fungus can be saprophytic, in which there are no symptoms and the fungus simply co-exists in the ear canal in a harmless parasitic relationship with the host, in which case the only physical finding is presence of the fungus. If for any reason the fungus begins active reproduction, the ear canal can fill with dense fungal debris, causing pressure and ever-increasing pain that is unrelenting until the fungus is removed from the canal and anti-fungal medication is used. Most antibacterial ear drops also contain a steroid to hasten resolution of canal edema and pain. Unfortunately such drops make fungal infection worse. Prolonged use of them promotes growth of fungus in the ear canal. Antibacterial ear drops should be used a maximum of one week, but 5 days is usually enough. Otomycosis responds more than 95% of the time to a three day course of the same over-the-counter anti-fungal solutions used for athlete's foot.

Pathogens

The majority of cases are due to Pseudomonas aeruginosa, followed by a great number of other gram-positive and gram-negative species.^[9] Candida albicans and Aspergillus species are the most common fungal pathogens responsible for the condition.

Diagnosis

When the physician looks in the ear, the canal appears red and swollen in well-developed cases of acute external otitis. The ear canal may also appear eczema-like, with scaly shedding of skin. Touching or moving the outer ear increases the pain, and this maneuvre on physical exam is very important in establishing the clinical diagnosis. It may be difficult for the physician to see the eardrum with an otoscope at the initial examination because of narrowing of the ear canal from inflammation and the presence of drainage and debris. Sometimes the diagnosis of external otitis is presumptive and return visits are required to fully examine the ear. Culture of the drainage may identify the bacteria or fungus causing infection, but is not part of the routine diagnostic evaluation. In severe cases of external otitis, there may be swelling of the lymph node(s) directly beneath the ear.

The diagnosis may be missed in most early cases because the examination of the ear, with the exception of pain with manipulation, is normal or nearly normal. In some cases of early external otitis, the most striking visual finding in the ear canal is the lack of cerumen. As a moderate or severe case of external otitis resolves, weeks may be required before the ear canal again shows a normal amount of cerumen. (wax)