Ушная сера: состав, функции и типы

Waxy substance secreted by the ear

Earwax, also known by the medical term cerumen, is a waxy substance secreted in the ear canal of humans and other mammals. Earwax can be many colors, including brown, orange, red, yellowish, and gray. Earwax protects the skin of the human ear canal, assists in cleaning and lubrication, and provides protection against bacteria, fungi, particulate matter, and water. 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 long chain fatty acids, both saturated and unsaturated, alcohols, squalene, and cholesterol. Earwax also contains dead skin cells and hair. Excess or compacted cerumen is the buildup of ear wax causing a blockage in the ear canal 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.

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. 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 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 audiologists and otorhinolaryngologists (ear, nose, and throat doctors).

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.

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.

Earwax helps protect the ear by trapping dust and other foreign particles that could filter through and damage the eardrum. Excessive earwax may impede the passage of sound in the ear canal, causing mild conductive hearing loss, pain in the ear, itchiness, or dizziness. Untreated impacted wax can result in hearing loss, social withdrawal, poor work function, and mild paranoia. People with impacted wax may also present with perforated eardrums; this is usually induced by putting objects in the ear in an attempt to remove the wax. by blocking earwax from leaving the ear canal. Earwax is estimated to be the cause of 60–80% of hearing aid faults. Excessive earwax can also cause tinnitus, a constant ringing in the ears, ear fullness, hearing loss and ear pain.

Movement of the jaw helps the ears' natural cleaning process. The American Academy of Otolaryngology discourages earwax removal, unless the excess earwax is symptomatic. While a number of methods of earwax removal are effective, their comparative merits have not been determined. A number of softeners are effective; however, if this is not sufficient, A curette method is more likely to be used by audiologists and otolaryngologists when the ear canal is partially occluded and the material is not adhering to the skin of the ear canal, but due to the high skill level needed to not damage the eardrum, is limited.

Microsuction involves the use of a vacuum suction probe to break up and extract impacted cerumen. Microsuction can be preferred over other methods as it avoids the presence of moisture in the ear, is often faster than irrigation, and is performed with direct vision of the earwax being removed. Typically, a camera with lights and guide hole is utilised, with a long metal vacuum probe being inserted into the guide hole the practitioner is then able to see inside the ear and remove earwax under pressure. Potential adverse effects include dizziness, temporary tinnitus, and reduced hearing due to volume of the pump and the proximity of the vacuum probe to the ear drum the frequency of these are reduced where the cerumen is softened in the five days preceding microsuction. In general, microsuction is well tolerated and even preferred by many patients.

Once the cerumen has been softened, it may be removed from the ear canal by irrigation, but the evidence on this practice is ambiguous. Ear syringing techniques are described in great detail by Wilson & Roeser 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, sodium bicarbonate solution, or a solution of water and vinegar to help prevent secondary infection. In the West, use of ear picks is usually only done by health professionals. Curetting earwax using an ear pick was common in ancient Europe and is still practised in East Asia. Since the earwax of most Asians is of the dry type, alternative medicine practice that involves a lighting a hollow candle and placing the unlit end in the ear canal. Advocates say that the dark residue appearing on the candle after the procedure consists of extracted earwax, but studies show that the same dark residue is left regardless of whether the candle is inserted into an ear, as the residue is derived from the candle itself and not the ear. The American Academy of Otolaryngology states that ear candles are not a safe option for removing ear wax, and that no controlled studies or scientific evidence support their use for ear wax removal. Survey responses from medical specialists (otolaryngologists) in the United Kingdom reported ear injuries including burns, ear canal occlusions and ear drum perforations and secondary ear canal infections with temporary hearing loss from ear candling.

A postal survey of British general practitioners Extrapolating from data obtained in Edinburgh, Sharp et al.

In medieval Europe, earwax and other substances such as urine were used to prepare pigments used by scribes to illustrate illuminated manuscripts. Pliny the Elder, in his Natural History, wrote that earwax—when applied topically—cured bites from humans, scorpions, and serpents; it was said to work best when taken from the ears of the wounded person itself. Early American lip balms may have been based on earwax. The 1832 edition of the American Frugal Housewife said that "nothing was better than earwax to prevent the painful effects resulting from a wound by a nail [or] skewer"; and also recommended earwax as a remedy for cracked lips. Before waxed thread was commonly available, a seamstress would use her own earwax to stop the cut ends of threads from fraying. Earwax retains concentrations of cortisol over time. As cortisol levels change throughout the day and increase in response to stress, long term measurements are difficult yet necessary. A 2020 study suggests swabbing earwax as a method of measuring long term cortisol levels that is noninvasive and does not confound itself.