Earwax

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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, fungus, and insects. A comprehensive review of the physiology and pathophysiology of cerumen can be found in Roeser and Ballachanda.^[1] Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing.

Contents 1 Production, composition, and different types 2 Function 2.1 Cleaning 2.2 Lubrication 2.3 Antibacterial and antifungal roles 3 Removal 3.1 Cerumenolysis 3.2 Syringing 3.3 Curette method 3.4 Hazards 3.5 Alternative practices 3.5.1 Ear candling 4 Earwax in whales 5 See also 6 References 7 External links

[edit] 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.^[2] The primary components of earwax are the final products in the HMG-CoA reductase pathway, namely, squalene, lanosterol, and cholesterol.

Two distinct genetically determined types of earwax are distinguished -- 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).^[3] Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit.^[4]

The difference in cerumen type has been tracked to a single base change (an SNP) 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.^[5]

[edit] Function

[edit] Cleaning

Cleaning of the ear canal occurs as a result of the "conveyor belt" process of epithelial migration, aided by jaw movement.^[6] 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 extrusion.

[edit] Lubrication

Lubrication prevents desiccation and itching 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.^[7][8]

[edit] Antibacterial and antifungal roles

While studies conducted up until the 1960s found little evidence supporting an antibacterial role for cerumen,^[9] 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.^[10][11] The growth of two fungi commonly present in otomycosis was also significantly inhibited by human cerumen.^[12] 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^[13]).

[edit] 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 repairs.^[14] 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 (used by 95% of GPs^[15]). A curette method is more likely to be used by otologists and ENTs when the ear canal is partially occluded and the material is not adhering to the skin of the ear canal.

[edit] Cerumenolysis

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.^[16] Other commercially available and common cerumenolytics include:

• [under multiple brand names] Carbamide peroxide (6.5%) and glycerine
• Sodium bicarbonate B.P.C. (sodium bicarbonate and glycerine)
• Various organic liquids (glycerol, almond oil, mineral oil, baby oil)
• Cerumol (arachis oil, turpentine and dichlorobenzene)
• Cerumenex (Triethanolamine, polypeptides and oleate-condensate)
• Exterol, Otex (UK brand name) (urea, hydrogen peroxide and glycerine)
• Docusate, an active ingredient found in laxatives

A cerumenolytic should be used 2-3 times daily for 3-5 days prior to the cerumen extraction.^[17] Although most commercially available cerumenolytics available in the U.S. are identical, containing carbamide peroxide (6.5%) and glycerine,^[17] a 10% solution of sodium bicarbonate 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.^[18] 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.

[edit] 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,^[17] and Blake et al.,^[19] 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 water,^[19] normal saline,^[20] sodium bicarbonate solution,^[21] or a solution of water and vinegar to help prevent secondary infection.^[19]

Patients generally prefer the irrigation solution to be warmed to body temperature,^[20] as dizziness is a common side effect of syringing with fluids that are colder or warmer than body temperature. Sharp et al.^[15] recommend 37 °C, while Blake et al.^[19] recommend using water at 38 °C, one degree above body temperature, and stress that this should be checked with a thermometer.

[edit] 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 and practiced in cases of serious blockage in the ear. However curetting earwax using an ear pick is common in East Asia and often done at home and also serves as an act to foster a sense of intimacy.^{[verification needed]} 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.

[edit] Hazards

A postal survey of British general practitioners^[15] 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 while the removal of cerumen is a commonplace procedure, it 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 educated and trained in the procedure.

Bull^[21] advised physicians: "After removal of wax, inspect thoroughly to make sure none remains. This advice might seem superfluous, but is frequently ignored." This was confirmed by Sharp et al.,^[15] who, in a survey of 320 general practitioners, found that only 68% of doctors bothered to inspect the canal after the syringing procedure 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.^[15]

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.^[19] 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.^[22] Extrapolating from data obtained in Edinburgh, Sharp et al.^[15] 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.

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.

It is generally advised not to use cotton swabs (Q-Tips or cotton buds) as these will likely push the wax further down the ear canal and, if used carelessly, perforate the eardrum. Also, the cotton head may fall off becoming lodged in the ear canal. Cotton swabs should be used only to clean the external ear.

[edit] Alternative practices

[edit] Ear candling

Main article: Ear candling

Ear candling, a folk medicine practice, is also used to remove ear wax and is claimed to 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 the toxins and wax. An earwax-like substance does indeed collect inside the ear candle as it burns - even if it is only placed in a clean, dry drinking glass. Ear candles are a fringe remedy in North America and Europe; skeptics argue its claimed benefits are not supported by scientific evidence.^[23] 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.^[24] Seely, Quigley and Langman reported that, in a survey of 122 ENT physicians, 21 ear injuries were reported due to ear candling ^[25]. 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"^[26].

[edit] 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.^[27]

[edit] See also

• Ear pick

[edit] References

[edit] External links

• Gooey earwax is in your genes, ABC Science Online, 30 January 2006
• Nicholas Wade. Scientists Find Gene That Controls Type of Earwax in People. The New York Times, 30 January 2006
• Dylan Stiles, What came out of my ear (composition of earwax), 7 August 2006