Timothy C. Hain, MD Page last modified: February 24, 2018
Otitis externa (OE) is an infection of external ear canal
Persons with OE present with pain, drainage and loss of hearing.
Otitis externa is most commonly caused by
Fungi (otomycosis) are usually accompanying organisms, but can be the primary cause of otitis media or otitis externa.
Mites (demodex) are found in roughly 6% of normal human ears and are more common in ears where a local steroid preparation has been used. (Cevlik et al, 2014). Ear mite infection is occasionally are associated with extremely itchy external otitis (Klem et al, 2009). This should not come as a surprise to pet owners who are familiar with ear mites.
Cultures of draining ears are recommended at the initial visit. However, the impact on management is uncertain.
- Meticulous cleaning using a microscope. This may require several visits.
- Ear drops are generally used to treat otitis externa.
- Presently most patients are started on a drop that contains a floroquinolone (e.g. ofloxacin), possibly with the addition of a steroid to reduce swelling (e.g. cipro HC).
- Note that recent reports have suggested that cipro-dexamethasone and ofloxacin-dexamethasone delays healing of the ear drum in rats (Dirain et al, 2018). The combination of quinolones such as ofloxacin and ciprofloxacin with steroids seems to be especially potent at retarding healing. Logic would suggest that a drop without a steroid, such as ofloxacin by itself, would be safer.
- An antibiotic pack may be used, using a 1/4" gauze (in an adult).
- If ear drops fail, then systemic antibiotics follow.
- Systemic antibiotics are not recommended as the first line of treatment (Hamerlynck et al., 2006).
- Because of the bacteriology of OE (staph, pseudomonas, MRSA, fungus, mites), somewhat unusual systemic antibiotics may be used.
- This may include high-dose trimethoprim sulfa (for MRSA).
Prevention measures for recurrence include the following (Sander, 2001)
- Avoid manipulation of ear canal (i.e. avoid putting things in the ear canal)
- Dry and clean ear
- Dry ears with hair dryer
- Boric acid powder dusting can be used to dry the ear (particularly with hearing aids)
- Clean ears in doctor's office with suction/microscope
- Acidification (2% acetic acid with hydrocortisone) -- Vosol is a brand name for this preparation. The usual dose is 3-4 drops in the affected ear three times/day. Not used in persons with perforation. See the comments below concerning cost.
When acidification fails, antifungal topical preparations are also commonly used. There are numerous of these agents used in animal medicine. None of these is presently FDA approved for human use and for this reason they are used "off-label" in humans. Several of these are available over-the-counter such as clotrimazole -- (Lotrimin AF) cream and tinactin solution. Use of these preparations should be under the supervision of a physician experienced in treating ear infections. Romsaithong et al (2016) reported that 1% clotrimazole solution was more effective than 3% boric acid in 70% alcohol.
Moshtaghi et al (2017) reviewed prices of ear drops in southern California, and stated:
"Data were collected from 108 pharmacies. The mean prices are noted for each of the individual drugs: Cortisporin (brand) 10 mL, $82.70; neomycin, polymyxin B sulfates, and hydrocortisone (Cortisporin-generic) 10 mL, $34.70; ofloxacin (generic) 10 mL, $99.95; sulfacetamide (generic) 15 mL, $40.18; Ciprodex (brand) 7.5 mL, $194.44; Cipro HC (brand) 10 mL, $233.32; Vosol (brand) 15 mL, $120.75; acetic acid (Vosol-generic) 10 mL, $116.55; VosolHC (brand) 10 mL, $204.14; acetic acid/aluminum acetate (Domeboro-generic) 60 mL, $22.91; and Tobradex (brand) 5 mL, $166.47."
As can be seen, the least expensive treatment, on average, is Domeboro-generic ($22.91). This is actually an antiseptic treatment, with the mechanism being making the ear canal more acidic. The safest in regards to lowered risk of hearing loss should there be a perforation, as well as the least painful treatment (in our opinion) is moderately expensive (ofloxacin generic -- $99.95). One wonders why a generic is so expensive in the US. Amazingly enough, drops made of acetic acid (e.g. Vosol-generic) cost $116.55. Considering the cost of the raw ingredients (i.e. vinegar and water), this seems high.
This is generally recognized by failure or partial response to treatment for acute external otitis. Typical organisms are candida and aspergillus. One should rule out metabolic and immunological disorders, i.e. diabetes, cancer chemotherapy, leukemia, and HIV among others. The ear should be carefully cleaned, and an anti-fungal cream such as Nizoral or Lotromin considered. There shold be repeat cleaning and application of the antifungal every 10-14 days. (Farrior, 2000)
Only a few cases have been reported of ear mites in humans. One paper reported treatment with topical hexachlorocyclohexane (Klemm et al, 2009). They suggested that a more contemporary treatment might be permethrin. These drugs are rarely used in humans and their effect is not well understood.