Impacted wax

Earwax, also known by the medical term cerumen, is a gray, orange, red or yellowish waxy substance secreted in the ear canal of humans and other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, and also provides protection against bacteria, fungi, insects, and water. Earwax consists of shed skin cells, hair, and the secretions of the ceruminous and sebaceous glands of the outside ear canal. Major components of earwax are long chain fatty acids, both saturated and unsaturated, alcohols, squalene, and cholesterol. Excess or compacted cerumen can press against the eardrum or block the outside ear canal or hearing aids, potentially causing hearing loss. Cerumen is produced in the outer third of the cartilaginous portion of the ear canal. It is a mixture of viscous secretions from sebaceous glands and less-viscous ones from modified apocrine sweat glands. The primary components of 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. There are two distinct genetically determined types of earwax: the wet type, which is dominant, and the dry type, which is recessive. While East Asians and Native Americans are more likely to have the dry type of cerumen (gray and flaky), African and European people are more likely to have the wet type (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. Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit. In Japan, wet-type earwax is more prevalent among the Ainu, in contrast to that country's Yamato majority. The wet type earwax differs biochemically from the dry type mainly by its higher concentration of lipid and pigment granules; for example the wet type is 50% lipid while the dry type is only 20%. A specific gene has been identified that determines whether people have wet or dry earwax. 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', specifically rs17822931. Dry-type individuals are homozygous for adenine whereas wet-type requires at least one guanine. Wet-type earwax is associated with armpit odor, which is increased by sweat production. Researchers have conjectured that the reduction in sweat or body odor was beneficial to the ancestors of East Asians and Native Americans who are thought to have lived in cold climates. Cleaning of the ear canal occurs as a result of the 'conveyor belt' process of epithelial migration, aided by jaw movement. Cells formed in the centre of the tympanic membrane migrate outwards from the umbo (at a rate comparable to that of fingernail growth) to the walls of the ear canal, and move towards the entrance of the ear canal. The cerumen in the ear canal is also carried outwards, taking with it any 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. Removing earwax is in the scope of practice for audiologists and otorhinolaryngologists (ear, nose, and throat) doctors. The lubrication provided by cerumen prevents desiccation of the skin within the ear canal. The lubricative properties arise from the high lipid content of the sebum produced by the sebaceous glands. In wet-type cerumen, these lipids include cholesterol, squalene, and many long-chain fatty acids and alcohols. 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 normal 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.