Earwax

Earwax, also known by the medical term cerumen, is a 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 some protection from bacteria, fungi, insects and water. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing.

Physiology

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. The primary components of earwax are shed layers of skin, with 60% of the earwax consisting of keratin, 12–20% saturated and unsaturated long-chain fatty acids, alcohols, squalene and 6–9%cholesterol.

Fear, stress and anxiety result in increased production of earwax from the ceruminous glands.

There are two distinct genetically determined types of earwax: the wet type, which is dominant, and the dry type, which is recessive. WhileAsians and Native Americans are more likely to have the dry type of cerumen (gray and flaky), black and white people are more likely to have the wet type (honey-brown to dark-brown and moist). Cerumen type has been used by anthropologists to track human migratory patterns, such as those of the Inuit. Wet-type earwax is more prevalent among the Ainu of Japan, in contrast to Japanese people. The consistency of wet type earwax is due to the higher concentration of lipid and pigment granules (50% lipid) in the substance than the dry type (30% lipid).

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.

[edit]Cleaning

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 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.

[edit]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.

[edit]Antibacterial and antifungal 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 normal individuals).

[edit]Treatment

Movement of the jaw helps the ears' natural cleaning process. The American Academy of Otolaryngology discourages earwax removal unless excess earwax is causing health problems.  While a number of methods of earwax removal are effective, their benefits as compared to each other is not yet determined. A number of softeners are effective; however, if this is not sufficient, the most common method of cerumen removal is syringing with warm water.  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. Cotton swabs, on the other hand, push most of the earwax further into the ear canal and remove only a small portion of the top layer of wax that happens to adhere to the fibres of the swab.