Otitis externa ("swimmer's ear") is an inflammation of the outer ear and ear canal. Along with otitis media, external otitis is one of the
two human conditions commonly called "earache". It also occurs in many other species.
Inflammation of the skin of the ear canal is the essence of this disorder. The inflammation can be
secondary to dermatitis (eczema) only, with no microbial infection, or it can be caused by active bacterial or fungal infection.
In either case, but more often with infection, the ear canal skin swells and may become painful and/or tender to touch.
Chronic otitis externa is a low-grade disease, usually non-microbial and purely on the basis of chronic dermatitis or
irritation from "cleaning" the canal, often with cotton swabs. It can be thought of as chronic dermatitis of the ear canal skin
and may or may not be painful. There may only be seepage, mild swelling, or itching.
In contrast to the chronic otitis externa, acute otitis externa is predominantly a microbial infection, occurs rather
suddenly, rapidly worsens, and becomes very painful and alarming. The ear canal has an abundant nerve supply, so the pain is
often severe enough to interfere with sleep. Wax in the ear can combine with the swelling of the canal skin and any associated
pus to block the canal and dampen hearing to varying degrees, creating a temporary conductive hearing loss. In more severe or
untreated cases, the infection can spread to the soft tissues of the face that surround the adjacent parotid gland and the jaw
joint, making chewing painful. In its mildest forms, external otitis is so common that some ear nose and throat physicians have
suggested that most people will have at least a brief episode at some point in life. While a small percentage of people seem to
have an innate tendency toward chronic external otitis, most people can avoid external otitis altogether once they understand the
mechanisms of the disease.
The skin of the bony ear canal is unique, in that it is not movable but is closely attached to the bone, and it is almost
paper thin. For these reasons it is easily abraded or torn by even minimal physical force. Inflammation of the ear canal skin
typically begins with a physical insult, most often from injury caused by attempts at self-cleaning or scratching with cotton
swabs, hair pins, keys, or other small implements. Another causative factor for acute infection is prolonged water exposure in
the forms of swimming or exposure to extreme humidity, which can compromise the protective barrier function of the canal skin,
allowing bacteria to flourish; hence the name, "swimmer's ear". Densely impacted wax, usually caused by enthusiastic use of
cotton swabs, can put enough pressure on the ear canal skin to injure it and initiate infection. A sensation of blockage or
itching can prompt attempts to clean, scratch, or open the ear canal, which potentially worsens and perpetuates the condition.
The cotton fibers of a swab are abrasive to the thin, fixed canal skin. Self-manipulative measures to improve the condition often
make it worse and are to be discouraged, since it is a blind exercise that can result in significant injury to the ear.
Production of wax by glands in the canal may be hindered by external otitis. The exact function(s) of cerumen (earwax) is a
subject that is open to speculation, since there is very little research regarding its function. Some caretakers feel strongly
that earwax has a protective function with respect to infection and that a little earwax in the ear canal is a good thing. A
natural question is, "How can I clean my ears, then?" It is well established that in most people the top layer of the ear canal
skin normally migrates toward the ear opening, essentially sweeping the canal on a continuing basis. In other words, a normal ear
canal is self-cleaning. This self-cleaning physiologic feature fails in some patients, especially in late life, and periodic
cleaning by a physician can be necessary. The most controlled and least painful means of cleaning impacted wax or dead skin from
the ear canal is by using a binocular surgical microscope, which frees the examiner's hands to instrument the ear and provides
the magnification and depth perception needed to avoid traumatizing the delicate canal skin and eardrum.
There is an uncommon and serious form of external otitis called malignant or necrotizing external otitis, in which the
infection extends beyond the confines of the ear canal and can involve the bone of the skull. Although the name of this condition
contains the words "external otitis" it tends to follow a more severe and chronic clinical course and can lead to skull base
osteomyelitis. Instead of being a condition that most people are subject to, necrotizing external otitis (also called malignant
otitis externa) is a life-threatening disorder that only affects older individuals with diabetes and patients with major
disorders of the immune system. This uncommon complication of external otitis is discussed under Complications, below.[1]
Symptoms
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 (that 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.
Because the symptoms of external otitis promote many people to attempt to clean out the ear canal (or scratch it) with slim
implements, and self-cleaning attempts generally lead to additional trauma of the injured skin, rapid worsening of the condition
often occurs. Worsening is also common in the vacationer who continues holiday swimming despite symptoms of mild external
otitis.
Causes, incidence, and risk factors
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. 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. 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.[2]
Fungal ear canal infections, also known as otomycosis, range from inconsequential to very
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.
The incidence of otitis externa is high. In the Netherlands, it has been estimated at 12-14 per 1000 population per year, and
has been shown to affect more than 1% of a sample of the population in the United Kingdom over a 12 month period.[3]
Characteristics of the external ear leading to external otitis
The outer ear canal starts at the opening on each side of the head that allows the entry of sound; the skin-lined canal
extends in as far as the tympanic membrane (ear drum). The thin topmost layer of the ear canal skin is continuous with the
surface of the ear drum, forming its outermost layer. There are two distinct anatomical regions of the ear canal, the outer
portion, which lines the movable cartilage portion of the ear canal that is surrounded by soft tissues of the side of the head,
and the inner portion, which lines the bony ear canal that is part of the skull. The bony ear canal can be seen on preserved
specimens of the skull. The skin that is most easily injured, commonly giving rise to external otitis, is the delicate skin of
the inner portion, the thin closely applied skin of the bony ear canal, which is perhaps the only skin of the body that
ordinarily should never be touched!
The ear canal skin is specialized and is not like skin anywhere else on the body. The skin of the cartilaginous part of the
ear canal contains glands that make wax (cerumen), which is believed to have protective function(s). The skin of the bony portion
of the canal is almost paper thin, is firmly attached to bone, is immobile, and has no sweat glands. Like skin elsewhere on the
body, the surface layer of the canal skin sheds. Accumulation of shed debris is prevented by the self-cleaning mechanism of the
ear canal, with the top layer of the canal skin migrating outward along the canal to the surface of the head and bringing debris
with it. The outer ear canal skin has a thick layer of subcutaneous tissue cushioning it and is thus more resistant to injury
than the skin of the bony canal.
A folliculitis of one of the hairs of the outer portion of the ear canal can be the
start of a bout of external otitis. Impaction of cerumen that abuts up against the delicate skin of the bony canal, or attempts
to remove the impacted wax, can also be the initial event. Other inciting factors can be foreign bodies or cysts that develop in
the skin near or just inside the canal opening.
The S-shape of the ear canal, the presence of hair in the outer part, and the outward migration of skin all combine to help
shed water from the ear canal and keep shed skin from building up within the canal, as well as to keep water from pooling in the
innermost canal. In some minor malformations of the ear canal or auricle, the size and shape of the canal may pre-dispose
allowing water that enters the ear to remain, or to inhibit the normal shedding of superficial skin and cerumen from the ear canal. In such cases, the individual may have a predispostion to recurrent external
otitis.
Pathogens - The Disease-Causing Germs
The bacterial pathogens at the top of the list are Pseudomonas
aeruginosa and Staphylococcus aureus, followed by a great number
of other gram-positive and gram-negative species.[4]
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 maneuver 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 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.
Differentiating between otitis externa and otitis media
The second type of common "earache" is otitis media, and this inflammation of the
tympanic membrane and middle ear space is usually clinically
distinct from otitis externa. In a person with no history of chronic ear disease, acute otitis media seldom occurs in the absence
of a recent viral upper respiratory infection (URI), a common cold or flu. Most earaches are caused by either acute otitis
externa or by acute otitis media; it is very unusual to see both in the same ear at the same time. Importantly, persistent
earache without the physical findings of ear infection can be due to more serious, even lifethreatening, conditions, and should
always be investigated by an ear, nose, and throat physician (otolaryngologist). Acute otitis media and acute otitis externa are
easily confused because both can cause earache and drainage from the ear (otorrhea). In
middle ear infections, drainage only occurs if the tympanic membrane has a perforation or severe retraction pocket. When there is
chronic suppurative otitis media, with or without cholesteatoma, the drainage in the ear canal may appear identical to drainage from external otitis. The
primary distinction between acute otitis media and acute otitis externa is that otitis externa is characterized by swelling of
the ear canal skin, and there is increased pain on any pushing or pulling of the ear.
Monocular otoscopy, the most common means used by family physicians and pediatricians to
examine ears, has the severe limitation of providing no depth perception for the examiner. Uncertainty of the exact diagnosis can
lead to unnecessarily excessive prescribing to cover treatment for both otitis media and otitis externa. Differentiating external
otitis from otitis media is readily accomplished using a binocular microscope, which allows comfortable and safe cleaning of any
wax or debris in the ear canal, yielding a complete view of the visble parts of the ear canal and eardrum. Most otolaryngologists
(ear, nose, & throat physicians) have binocular microscopes in their offices and are trained to quickly accomplish this task,
increasing the likelihood of a correct, definitive diagnosis, which can then be treated appropriately. Cleaning of an infected
ear canal promotes better contact of the topical antibiotic drops and shortens recovery time. Children with surgically inserted
ear tubes who fail to keep water out of their ears often develop painless drainage from resulting bacterial otitis media. This is
not external otitis, but otitis media. It is painless because the opening maintained by the tube, assuming no obstructing crusts
or blood clot, prevents pressure from building up within the middle ear. This problem typically clears with antibiotic drops only
and does not require oral antibiotics.
Quinolone antibiotics in topical form (ear drops) have been shown to be of benefit in stopping discharge from otitis media
through an open eardrum, and so some treatments for otitis externa may be of benefit to otitis media.[5] The main pitfall of having a case of otitis media misdiagnosed as otitis externa
is that a serious infection of the middle-ear may have complications and sequelae over time.
Additionally, many types of topical ear drops that are safe and effective for use in the ear canal can be irritating and even
damaging if allowed past the ear drum into the more delicate internal membranes of the middle-ear, prompting the warning that
such topical preparations should not be used unless the tympanic membrane is known to be intact. For both reasons, caution
is given against self-treatment of "earache" without proper medical evaluation.
If there is prolonged drainage of noxious substances from the middle ear through the ear drum, then the skin of the ear canal
may become secondarily inflamed. In this situation, one that occurs only in individuals with severe chronic otitis media,
both external otitis and otitis media are present at that same time. Prolonged care by a qualified specialist is generally
required.
Treatment
The goal of treatment is to cure the infection and to return the ear canal skin to a healthy condition. When external otitis
is very mild, in its initial stages, simply refraining from swimming or washing hair for a few days, and keeping all implements
out of the ear, usually results in cure. For this reason, external otitis is called a self-limiting condition. However, if the
infection is moderate to severe, or if the climate is humid enough that the skin of the ear remains moist, spontaneous
improvement may not occur.
Topical solutions or suspensions in the form of ear drops are the mainstays of treatment for external otitis. Some contain
antibiotics, either antibacterial or antifungal, and others are simply designed to mildly acidify the ear canal environment to
discourage bacterial growth. Some prescription drops also contain anti-inflammatory steroids, which help to resolve swelling and
itching. Although there is evidence that steroids are effective at reducing the length of treatment time required, fungal otitis
externa (also called otomycosis) may be caused or aggravated by overly prolonged use of steroid-containing drops. In addition to
topical antibiotics, oral anti-pseudomonal antibiotics can be used in case of severe soft tissue swelling extending into the face
and neck and may hasten recovery.
Removal of debris (wax, shed skin, and pus) from the ear canal promotes direct contact of the prescribed medication with the
infected skin and shortens recovery time. This is best accomplished using a binocular microscope. When canal swelling has
progressed to the point where the ear canal is blocked, topical drops may not penetrate far enough into the ear canal to be
effective. The physician may need to carefully insert a wick of cotton or other commercially available, pre-fashioned, absorbent
material called an ear wick and then saturate that with the medication. The wick is kept saturated with medication until the
canal opens enough that the drops will penetrate the canal without it. Removal of the wick does not require a health
professional. Antibiotic ear drops should be dosed in a quantity that allows coating of most of the ear canal and used for no
more than 4 to 7 days. The ear should be left open. Do note that it is imperative that there is visualization of an intact
tympanic membrane. Use of certain medications with a ruptured tympanic membrane can cause
tinnitus, vertigo, dizziness and hearing loss in some cases.
Although the acute external otitis generally resolves in a few days with topical washes and antibiotics, complete return of
hearing and cerumen gland function may take a few more days. Once healed completely, the ear canal is again self-cleaning. Until
it recovers fully, it may be more prone to repeat infection from further physical or chemical insult.
Effective medications include ear drops containing antibiotics to fight infection, and corticosteroids to reduce itching
and inflammation. In painful cases a topical solution of antibiotics such as aminoglycoside, polymyxin or fluoroquinolone is
usually prescribed. Antifungal solutions are used in the case of fungal infections. External otitis is almost always
predominantly bacterial or predominantly fungal, so that only one type of medication is necessary and indicated.
The pain of acute otitis externa is often severe enough to interfere with sleep. Topical analgesic drops often prescribed by
primary care providers for pain relief are almost never adequate and should not be relied upon. A brief course of oral narcotic
pain medication is often necessary to maintain comfort while the antibiotic drops are working. Improvement with appropriate
initial treatment (cleaning of the canal, wick insertion if necessary, and antibiotic drops in adequate amount) is fairly rapid,
with pain improvement occurring within one day and resolution within 2-4 days. Heat application using a heating pad, can also aid
in pain relief.
Non-prescription remedies
Provided it is not too severe, recurrent otitis externa can often be successfully treated by non-prescription means, at low
cost. When symptoms recur in an individual who has had a previous diagnosis made, the use of non-prescription drops along
with precautions to keep water out of the ear is generally effective. Self-treatment with non-prescription remedies is dangerous
in individuals who have not been previously evaluated for the condition, because the tympanic
membrane may not be intact, and because the true condition may be otitis media with drainage. Drops and water precautions
may actually resolve otitis media with drainage for a period of time, while allowing an undiagnosed cholesteatoma to progress, or complications of otitis media to develop.
Effective solutions for the ear canal include acidifying and drying agents, used either singly or in combination. When the ear
canal skin is inflamed from the acute otitis externa, the use of dilute acetic acid may be
painful.
Burow's solution is an effective remedy against both bacterial and fungal external
otitis. This is a buffered mixture of aluminum sulfate and acetic acid, and is available without prescription in the United States.[6]
Prevention
The strategies for preventing acute external otitis are similar to those for treatment.
- Avoid inserting anything into the ear canal; use of Q tips is the most common event leading to acute otitis
externa.
- Most normal ear canals have a self-cleaning and self-drying mechanism, the latter by simple evaporation.
- After prolonged swimming, a person prone to external otitis can dry the ears using a small battery-powered ear dryer,
available at many retailers, especially shops catering to watersports enthusiasts. Alternatively, drops containing dilute acetic
acid (vinegar diluted 3:1) or Burow's solution may be used. It is especially important NOT to instrument ears when the skin is
saturated with water, as it is very susceptible to injury, which can lead to external otitis.
- Avoid swimming in polluted water.
- Avoid washing hair or swimming if very mild symptoms of acute external otitis begin
- Although the use of earplugs when swimming and shampooing hair may help prevent external
otitis, there are important details in the use of plugs. Hard and poorly fitting ear plugs can scratch the ear canal skin and set
off an episode. When earplugs are used during an acute episode, either disposable plugs are recommended, or used plugs must be
cleaned and dried properly to avoid contaminating the healing ear canal with infected discharge. One simple method of fabricating
soft waterproof disposable ear plugs is with cotton balls and petroleum jelly. These jelly coated cotton balls are NOT inserted
into the ear canal, but pressed into the auricle to cover the opening of the canal.
Prognosis
Otitis externa responds well to treatment, but complications may occur if it is not treated. Individuals with underlying
diabetes or disorders of the immune system are more likely to get complications,
including malignant otitis externa. In these individuals, rapid examination by an otolaryngologist (ear, nose, and throat
physician) is very important.
Complications
- Chronic otitis externa
- Spread of infection to other areas of the body
- Necrotizing External Otitis
Necrotizing External Otitis (Malignant otitis externa)
This uncommon form of external otitis occurs mainly in an elderly diabetics, being somewhat more likely and more severe when
the diabetes is poorly controlled. Even less commonly, it can develop due to a severely compromised immune system. Beginning as
infection of the external ear canal, there is extension of infection into the bony ear canal and the soft tissues deep to the
bony canal. The hallmark of malignant otitis externa (MOE) is unrelenting pain that interferes with sleep and persists even after
swelling of the external ear canal may have resolved with topical antibiotic treatment. MOE follows a more chronic course than
ordinary acute otitis externa. There may be granulation involving the floor of the external ear canal, most often at the
bony-cartilaginous junction. Paradoxically, the physical findings of MOE, at least in its early stages, are often much less
dramatic than those of ordinary acute otitis externa. In later stages there can be soft tissue swelling around the ear, even in
the absence of significant canal swelling. Unlike ordinary otitis externa, MOE requires oral or intravenous antibiotics for cure.
Diabetes control is also an essential part of treatment. When MOE goes unrecognized and untreated, the infection continues to
smolder and over weeks or months can spread deeper into the head and involve the bones of the skull base, constituting skull base
osteomyelitis (SBO). The infecting organism is almost always pseudomonas aeruginosa, but it can instead be fungal (aspergillus or
mucor). MOE and SBO are not amenable to surgery, but exploratory surgery may facilitate culture of unusual organism(s) that are
not responding to empirically used anti-pseudomonal antibiotics. The usual surgical finding is diffuse cellulitis without
localized abscess formation. SBO can extend into the petrous apex of the temporal bone or more inferiorly into the opposite side
of the skull base. As the skull base is progressively involved, the adjacent exiting cranial nerves and their branches,
especially the facial nerve and the vagus nerve, may be affected, resulting in facial paralysis and hoarseness, respectively. If
both of the recurrent laryngeal nerves are paralyzed, shortness of breath may develop and necessitate tracheotomy. Profound
deafness can occur, usually later in the disease course due to relative resistance of the inner ear structures. Gallium scans are
sometimes used to document the extent of the infection but are not essential to disease management. Skull base osteomyelitis is a
chronic disease that can require months of IV antibiotic treatment, tends to recur, and has a significant mortality rate.
References
- ^ Beers S, Abramo T (2004). "Otitis externa
review.". Pediatr Emerg Care 20 (4): 250-6. PMID 15057182.
- ^ Kang K, Stevens SR. Pathophysiology of atopic dermatitis. Clin Dermatol
2003;21:116–121.
- ^ van Balen F, Smit W, Zuithoff N, Verheij T
(2003). "Clinical efficacy of three common treatments in acute otitis externa in primary care: randomised controlled trial.".
BMJ 327 (7425): 1201-5. PMID 14630756. Full text
- ^ Roland P, Stroman D (2002). "Microbiology
of acute otitis externa.". Laryngoscope 112 (7 Pt 1): 1166-77. PMID 12169893.
- ^ Macfadyen CA. Acuin JM. Gamble C. Topical antibiotics without steroids for
chronically discharging ears with underlying eardrum perforations. [Review] [157 refs] [Journal Article. Meta-Analysis. Review]
Cochrane Database of Systematic Reviews. (4):CD004618, 2005.
- ^ Kashiwamura M. Chida E. Matsumura M. Nakamaru Y. Suda N. Terayama Y. Fukuda
S. The efficacy of Burow's solution as an ear preparation for the treatment of chronic ear infections. [Clinical Trial. Journal
Article] Otology & Neurotology. 25(1):9-13, 2004
See also
External links
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