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Earwax

Waxy substance secreted by the ear

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Through Bacteria, Fungus and Secretion

Major components of earwax include cerumen, produced by a type of modified sweat gland, and sebum, an oily substance. Both components are made by glands located in the outer ear canal. The chemical composition of earwax includes saturated and unsaturated long chain fatty acids, alcohols, squalene, and cholesterol. Earwax also contains dead skin cells and hair.

Excess or compacted cerumen is the buildup of earwax causing a blockage in the ear canal and it can press against the eardrum or block the outside ear canal or hearing aids, potentially causing hearing loss.

Physiology

Cerumen is produced in the cartilaginous outer third portion of the ear canal. It is a mixture of secretions from sebaceous glands and less-viscous ones from modified apocrine sweat glands. The primary components of both wet and dry earwax are shed layers of skin, with, on average, 60% of the earwax consisting of keratin, 12–20% saturated and unsaturated long-chain fatty acids, alcohols, squalene and 6–9% cholesterol.

Wet or dry

There are two genetically-determined types of earwax: the wet type, which is dominant, and the dry type, which is recessive. This distinction is caused by a single base change in the "ATP-binding cassette C11 gene". Dry-type individuals are homozygous for adenine (AA) whereas wet-type requires at least one guanine (AG or GG). Dry earwax is gray or tan and brittle, and is about 20% lipid. It has a smaller concentration of lipid and pigment granules than wet earwax. Wet earwax is light brown or dark brown and has a viscous and sticky consistency, and is about 50% lipid. Wet-type earwax is associated with armpit odor, which is increased by sweat production.

Some East Asians (including Yamato Japanese), Southeast Asians and Native Americans (including Inuit) are more likely to have the dry type of earwax (gray and flaky), while Africans, Europeans, and other East Asians (including Ainu) are more likely to have wet type earwax (honey-brown, dark orange to dark-brown and moist). 30–50% of South Asians, Central Asians and Pacific Islanders have the dry type of cerumen.

Cleaning

Cleaning of the ear canal occurs as a result of the "conveyor belt" process of epithelial migration, aided by jaw movement. From the umbo, cells formed in the center of the tympanic membrane move to the walls of the ear canal, and then towards the entrance of the ear canal. The cerumen in the ear canal is also carried outwards, taking with it particulate matter that may have gathered in the canal. Jaw movement dislodges debris from the walls of the ear canal to assist in this process.

Removing earwax is in the scope of practice for nurses, audiologists, Family Medicine physicians, and otorhinolaryngologists (ear, nose, and throat doctors).

Lubrication

The lubrication provided by cerumen prevents drying of the skin within the ear canal. The high lipid content of the sebum produced by the sebaceous glands causes the cerumen to work like lubrication. In wet-type cerumen, these lipids include cholesterol, squalene, and many long-chain fatty acids and alcohols.

Antimicrobial effects

While studies conducted up until the 1960s found little evidence supporting antibacterial activity for cerumen, more recent studies have found that cerumen has a bactericidal effect on some strains of bacteria. Cerumen has been found to reduce the viability of a wide range of bacteria, including Haemophilus influenzae, Staphylococcus aureus, and many variants of Escherichia coli, sometimes by as much as 99%. The growth of two fungi commonly present in otomycosis was also significantly inhibited by human cerumen. These antimicrobial properties are due principally to the presence of saturated fatty acids, lysozyme and, especially, to the slight acidity of cerumen (pH typically around 6.1 in average individuals). Conversely, other research has found that cerumen can support microbial growth and some cerumen samples were found to have bacterial counts as high as 107/g cerumen. The bacteria were predominantly commensals.

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