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==References==
==References==
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==External links==
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Revision as of 21:15, 6 February 2013

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Overview

Earwax, also known by the medical term cerumen, is a yellowish, waxy substance secreted in the ear canal of humans and many other mammals. It plays an important role in the human ear canal, assisting in cleaning and lubrication, and also provides some protection from bacteria, fungi, and insects. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing.

Production, composition, and different types

Cerumen is produced in the outer third of the cartilaginous portion of the human ear canal. It is a mixture of viscous secretions from sebaceous glands and less-viscous ones from modified apocrine sweat glands.[1] The primary components of earwax are the final products in the HMG-CoA reductase pathway, namely, squalene, lanosterol, and cholesterol.

There are two distinct genetically determined types of earwax: the wet type, which is dominant, and the dry type, which is recessive. Asians and Native Americans are more likely to have the dry type of cerumen (grey and flaky), whereas Caucasians and Africans are more likely to have the wet type (honey-brown to dark-brown and moist).[2] Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit.[3]

The difference in cerumen type has been tracked to a single base change (a single nucleotide polymorphism) in a gene known as "ATP-binding cassette C11 gene". In addition to affecting cerumen type, this mutation also reduces sweat production. The researchers conjecture that the reduction in sweat was beneficial to the ancestors of East Asians and Native Americans who are thought to have lived in cold climates.[4]

Function

Cleaning

Cleaning of the ear canal occurs as a result of the "conveyor belt" process of epithelial migration, aided by jaw movement.[5] Cells formed in the centre of the tympanic membrane migrate outwards from the umbo (at a rate equivalent to that of fingernail growth) to the walls of the ear canal, and accelerate towards the entrance of the ear canal. The cerumen in the canal is also carried outwards, taking with it any dirt, dust, and particulate matter that may have gathered in the canal. Jaw movement assists this process by dislodging debris attached to the walls of the ear canal, increasing the likelihood of its expulsion.

Lubrication

Lubrication prevents desiccation, itching, and burning of the skin within the ear canal (known as asteatosis). The lubricative properties arise from the high lipid content of the sebum produced by the sebaceous glands. In wet-type cerumen at least, these lipids include cholesterol, squalene, and many long-chain fatty acids and alcohols.[6][7]

Antibacterial and antifungal roles

While studies conducted up until the 1960s found little evidence supporting an antibacterial role for cerumen,[8] more recent studies have found that cerumen has a bactericidal effect on some strains of bacteria. Cerumen has been found to be effective in reducing the viability of a wide range of bacteria (sometimes by up to 99%), including Haemophilus influenzae, Staphylococcus aureus, and many variants of Escherichia coli.[9][10] The growth of two fungi commonly present in otomycosis was also significantly inhibited by human cerumen.[11] These antimicrobial properties are due principally to the presence of saturated fatty acids, lysozyme and, especially, to the relatively low pH of cerumen (typically around 6.1 in normal individuals[12]).

Removal

Excessive cerumen may impede the passage of sound in the ear canal, causing conductive hearing loss. It is also estimated to be the cause of 60–80% of hearing aid faults.[13] As mentioned above, movement of the jaw helps the ears' natural cleaning process, so chewing gum and talking can both help. If this is insufficient, the most common method of cerumen removal by general practitioners is syringing with warm water (used by 95% of GPs[14]). A curette method is more likely to be used by otolaryngologists when the ear canal is partially occluded and the material is not adhering to the skin of the ear canal.

Cerumenolysis

In cases of those who have the "wet-type" of earwax, it is usually necessary to soften wax before its removal. This process is referred to as cerumenolysis, and is achieved using a solution known as a cerumenolytic agent which is introduced into the ear canal. The most common home-remedy for this purpose is olive oil.[15] Other commercially available and common cerumenolytics include:

A cerumenolytic should be used 2-3 times daily for 3-5 days prior to the cerumen extraction.[16] Although most commercially available cerumenolytics available in the U.S. are identical, containing carbamide peroxide (6.5%) and glycerine,[16] a 10% solution of sodium bicarbonate (baking soda) was found to be a more effective cerumenolytic than several commercially-available solutions (Cerumenex, Auralgan) and numerous organic liquids, including glycerine, olive oil, and alcohol.[17] Additionally, 1 mL of docusate was also found to be a more effective cerumenolytic than several commercially-available solutions (Cerumenex, Debrox) [1]. Docusate may be extracted from liquid preparations of laxatives, such as Colace.

A systematic review of studies of the effectiveness of topical preparations for the treatment of earwax[2] concluded that cerumenolysis is better than no treatment, but there is little to choose between oil- and water-based preparations (including plain water). Applying such a preparation half an hour before syringing is probably as effective as applying it for several days. Several days' treatment with some preparations not based on water or oil appears promising. More studies are needed.

Syringing

Once the cerumen has been softened, it may be removed from the ear canal by irrigation. Ear syringing techniques are described in great detail by Wilson & Roeser,[16] and Blake et al.,[18] who advise pulling the external ear up and back, and aiming the nozzle of the syringe slightly upwards and backwards so that the water flows as a cascade along the roof of the canal. The irrigation solution flows out of the canal along its floor, taking wax and debris with it. The solution used to irrigate the ear canal is usually warm water,[18] normal saline,[19] sodium bicarbonate solution,[20] or a solution of water and vinegar to help prevent secondary infection.[18]

Patients generally prefer the irrigation solution to be warmed to body temperature,[19] as dizziness is a common side effect of syringing with fluids that are colder or warmer than body temperature. Sharp et al.[14] recommend 37 °C, while Blake et al.[18] recommend using water at 38 °C, one degree above body temperature, and stress that this should be checked with a thermometer.

A syringe should be used to gently stream water into the ear. For children the rate and speed should be lower. After irrigating, tip the head to allow the water to drain. Irrigation may need to be repeated several times. If the water stream hurts then the flow should be slower. It is better to irrigate too gently for a long period than irrigate too forcefully attempting to remove wax quickly. This procedure can be done at home in the shower using a self-use ear irrigation syringe with a right angle tip. After the wax is removed, the ear can be dried tipping the head then gently pulling the ear upwards to straighten the ear canal. If this does not remove enough water, the ear can be dried with a hair dryer set on low.

Curette method

The earwax is removed through the use of an ear pick, which physically dislodges the earwax and scoops it out of the ear canal. In the west, use of a curette or ear pick is often only done in the hands of health professionals; a modified curette having a safety stop to prevent deep insertion for self-use is available. Curetting earwax using an ear pick is common in East Asia. As the earwax of most East Asians is of the dry type, it is extremely easy to remove all earwax via light scraping with an ear pick as it simply falls out in large pieces or dry flakes, often on it's own.

Hazards

A postal survey of British general practitioners[14] found that only 19% always performed the procedure themselves; many delegated the task to practice nurses, some of whom had received no instruction. This is problematic as the removal of cerumen is not without risk. Irrigation can be performed at home with proper equipment as long as the person is careful not to irrigate too hard. All other methods should only be carried out by individuals who have been sufficiently trained in the procedure.

Bull advised physicians: "After removal of wax, inspect thoroughly to make sure none remains. This advice might seem superfluous, but is frequently ignored."[20] This was confirmed by Sharp et al.,[14] who, in a survey of 320 general practitioners, found that only 68% of doctors inspected the ear canal after syringing to check that the wax was removed. As a result, failure to remove the wax from the canal made up approximately 30% of the complications associated with the procedure. Other complications included otitis externa, pain, vertigo, tinnitus, and perforation of the ear drum. Based on this (single) study, a rate of major complications in 1/1000 ears syringed was suggested.[14]

Claims arising from ear syringing mishaps account for about 25% of the total claims received by New Zealand's Accident Compensation Corporation ENT Medical Misadventure Committee.[18] While high, this is not surprising, as ear syringing is an extremely common procedure. Grossan suggested that approximately 150,000 ears are irrigated each week in the United States, and about 40,000 per week in the United Kingdom.[21] Extrapolating from data obtained in Edinburgh, Sharp et al.[14] place this figure much higher, estimating that approximately 7000 ears are syringed per 100,000 population per annum. In the New Zealand claims mentioned above, perforation of the tympanic membrane was by far the most common injury resulting in significant disability.

Cotton swabs

It is generally advised not to use cotton swabs (Q-Tips or cotton buds) as these will likely push the wax farther down the ear canal and, if used carelessly, perforate the eardrum. Abrasion of the ear canal, particularly after water has entered from swimming or bathing, can lead the way to ear infection. Also, the cotton head may fall off and become lodged in the ear canal. Cotton swabs should be used only to clean the external ear.

Alternative practices

Ear candling

Ear candling, a folk medicine practice, is claimed to remove ear wax and improve ear health. It involves placing a hollow candle in the ear canal and lighting it; the rising hot air is believed to pull out wax and "toxins" from the ear. An earwax-like substance does indeed collect inside the ear candle as it burns - but it collects there even if the candle is placed in a clean, dry drinking glass instead of on an ear. Ear candles are a fringe remedy in North America and Europe, but the claimed benefits are not supported by scientific evidence.[22] Ear candles can also drip hot melted candle wax inside a person's ear; if the hot wax lands on the eardrum, it can cause great pain and possible hearing damage.[23] Seely, Quigley and Langman reported that, in a survey of 122 ENT physicians, 21 ear injuries were reported due to ear candling.[24] Ernst, in a review of the literature, finds that ear candling has no real effect on earwax removal, and poses a danger of ear injuries. He concludes that ear candling is "a triumph of ignorance over science".[25] Ear candles also deposit candle wax into the bottom of the ear candle tube, which can be interpreted as ear wax, but is simply brown wax from the candle.

Earwax in whales

Many species of whale have an annual buildup of earwax, adding one, two, or four layers (depending upon the species) each year. Similar to the incremental dating method of dendrochronology for trees, the number of layers can be counted to determine the age of the whale after its death.[26]

See also

Further reading

A comprehensive review of the physiology and pathophysiology of earwax can be found in a 1997 review article by Roeser and Ballachanda.[27] See also the New York Times article on the Yoshiura earwax study.[28]

References

  1. ↑ Alvord, L.S., Farmer, B.L. (1997). "Anatomy and orientation of the human external ear". J.Am.Acad.Audiol. 8 (6): 383–390. PMID 9433684.
  2. ↑ Overfield, T. (1985). Biologic Variation in Health and Illness: Race, Age, and Sex Differences. Menlo Park, CA, USA: Addison-Wesley Publishing. ISBN 0-201-12810-1.
  3. ↑ Bass, E.J., Jackson, J.F. (1977). "Cerumen types in Eskimos". Am.J.Phys.Anthropol. 47 (2): 209–210. PMID 910884.
  4. ↑ Yoshiura, K.I.; et al. (29 January 2006). "A SNP in the ABCC11 gene is the determinant of human earwax type". Nat Genet. doi:10.1038/ng1733.
  5. ↑ Alberti, P.W.R.M. (1964). "Epithelial migration on the tympanic membrane". J.Laryngol.Otol. 78: 808–830. PMID 14205963.
  6. ↑ Harvey, D.J. (1989). "Identification of long-chain fatty acids and alcohols from human cerumen by the use of picolinyl and nicotinate esters". Biomed.Environ.Mass.Spectrom. 18 (9): 719–723. PMID 2790258.
  7. ↑ Bortz, J.T., Wertz, P.W., Downing, D.T. (1990). "Composition of cerumen lipids". J.Am.Acad.Dermatol. 23 (5): 845–849. PMID 2254469.
  8. ↑ Perry, E.T., Nichols, A.C. (1956). "Studies on the growth of bacteria in the human ear canal". J.Invest.Dermatol. 27 (3): 165–170. PMID 13367525.
  9. ↑ Chai TJ, Chai TC. (1980). "Bactericidal activity of cerumen". Antimicrob Agents Chemother. 18 (4): 638–641. PMID 7447422.
  10. ↑ Stone, M., Fulghum, R.S. (1984). "Bactericidal activity of wet cerumen". Ann Otol Rhinol Laryngol. 93 (2): 183–186. PMID 6370076.
  11. ↑ Megarry, S., Pett, A., Scarlett, A., Teh, W., Zeigler, E., Canter, R.J. (1988). "The activity against yeasts of human cerumen". J.Laryngol.Otol. 102 (8): 671–672. PMID 3047287.
  12. ↑ Roland, P.S., Marple, B.F. (1997). "Disorders of the external auditory canal". J.Am.Acad.Audiol. 8 (6): 367–378. PMID 9433682.
  13. ↑ Oliveira, R.J. (1997). "The active earcanal". J Am Acad Audiol. 8 (6): 401–410. PMID 9433686.
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 Sharp, J.F., Wilson, J.A., Ross, L., Barr-Hamilton, R.M. (1990). "Ear wax removal: A survey of current practice". Br.Med.J. 301 (6763): 1251–1253. PMID 2271824.
  15. ↑ Fraser J.G. (1970). "The efficacy of wax solvents, in vitro studies and clinical trial". J.Laryngol.Otol. 84 (10): 1055–1064. PMID 5476901.
  16. ↑ 16.0 16.1 16.2 Wilson, P.L., Roeser, R.J. (1997). "Cerumen management: professional issues and techniques". J.Am.Acad.Audiol. 8 (6): 421–430. PMID 9433688.
  17. ↑ Robinson, A.C., Hawke, M. (1989). "The efficacy of ceruminolytics: everything old is new again". J.Otolaryngol. 18 (6): 263–267. PMID 2555535.
  18. ↑ 18.0 18.1 18.2 18.3 18.4 Blake, P., Matthews, R., Hornibrook, J. (1998). "When not to syringe an ear". N.Z.Med.J. 111 (1077): 422–424. PMID 9861921.
  19. ↑ 19.0 19.1 Ernst, A.A., Takakuwa, K.M., Letner, C., Weiss, S.J. (1999). "Warmed versus room temperature saline solution for ear irrigation: a randomised clinical trial". Ann.Emerg.Med. 34 (3): 347–350. PMID 10459091.
  20. ↑ 20.0 20.1 Bull, P.D. (1985). Lecture notes on diseases of the ear nose and throat (6th edition ed.). Oxford: Blackwell Scientific Publications. ISBN 0-632-06506-0.
  21. ↑ Grossan, M. (1998). "Cerumen removal – current challenges". Ear Nose Throat J. 77 (7): 541–548. PMID 9693470.
  22. ↑ Carroll, R.T. (2005). "The Skeptic's Dictionary: ear candling (coning)". Unknown parameter |accessdaymonth= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  23. ↑ Adams, Cecil (1995). "The Straight Dope: How do "ear candles" work?". Unknown parameter |accessdaymonth= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  24. ↑ Seely, D.R., Quigley, S.M., Langman, A.W. (1996). "Ear candles - efficacy and safety". Laryngoscope. 106 (10): 1226–1229. PMID 8849790.
  25. ↑ Ernst, E. (2004). "Ear candles: A triumph of ignorance over science". J. Laryngol. Otol. 118 (1): 1–2. PMID 14979962.
  26. ↑ Commanding Officer of NOAA Ship MALCOLM BALDRIGE
  27. ↑ Roeser, R.J., Ballachanda, B.B. (1997). "Physiology, Pathophysiology, and Anthropology/Epidemiology of Human Earcanal Secretions". J.Am.Acad.Audiol. 8 (6): 391–400. PMID 9433685.
  28. ↑ Wade, Nicholas (2006). "Japanese Scientists Identify Ear Wax Gene". New York Times. Unknown parameter |month= ignored (help); Unknown parameter |day= ignored (help)

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