By Dr. Max S. Chartrand Ph.D.
The Role of Keratin in the External Ear Canal
The keratin layer of tissue of the external ear canal is made up of inorganic protein (no circulatory or neurological system), similar in chemistry to human hair. It lies across the top of the ear canal from the aperture of the ear canal all the way to the tympanic membrane, and has a "shiny" consistency, often bunching up into "lines", as underlying tissue grows outward from the tympanic membrane. Keratin tissues are what shields the ear canal from bacteria, fungus, yeast, amoeba, and septic debris, allowing the epithelium, the outer layer of skin tissue, to maintain proper pH and to maintain overall external ear health. Hence, keratin is the protective layer over the skin of the ear canal, without which the ear canal would be totally susceptible to invasion, injury, and/or disease. This layer also shields the sensitive neural reflexes arising from myelinated and unmyelinated nerve fibers of Cranial V, VII, IX, X that innervate the external canal, which can cause complications in many hearing aid and earmold fittings.
The natural desquamation of tissue in the ear canal is such that tissue grows outward from near the umbo (or center point of the eardrum) on out to the aperture of the ear canal. This natural process generally takes about three months to travel the full length of the canal, though migration of specific cells may be uneven. So, that if one were to place a piece of sand on the tympanic eardrum today, about three months from now they will reach up and with fingertip remove the same piece of sand in the bowl or concha of the ear. Left undisturbed, then, healthy ear canals are self-cleaning and wax impaction is rare.
The sad truth is that keratin (or keratinocytes) in modern day society gets a short shrift, whether via personal care habits (Q-tips, boric acid ear drops, scratching with various objects) or via allopathic medical treatment (ear cleaning methods, most ear medications, etc.) Without keratin intact on the canal, for instance, ceruminous and sebaceous substances do not form properly into earwax and the canal's pH drops. This often leaves the canal dry with a host of extant skin problems (psoriasis, eczema, external otitis, contact dermatitis, allergy, and abnormal cell growth, such as basal and squamous cell carcinomas). Formation of keratin requires about 10-14 days for a layer of removed keratin to replace itself, provided the underlying skin tissue does not become infected, dry or loses its essential pH in the meantime. The problem is that boric or acetic acid or hydrogen peroxide solutions not only remove keratin and epithelium, they also dry out the skin, setting the external meatus up for infection. Furthermore, these acids inhibit cerumen production, as well as prohibiting the natural desquamation of tissue and regeneration of the badly needed keratin. Unfortunately, such harsh solutions are the mainstay of today's otopharmacopia. Readers may wish to explore other more gentle, natural approaches to softening hardened earwax.
For the reader who desires more in depth information about the physiology of the external ear, I refer them to the following sources:
Johnson, A. and Hawke, M., "The nonauditory physiology of the external ear canal", from Physiology of the Ear, eds. Jahn, A.F., and Santos-Sacchi, J., Raven Press: New York, pp 41-58, 1988.
Chartrand, M.S., "Basic Course in External Ear Care", Hearing Library, www.digicare.org, 2002.
Chartrand, M.S. "Observation & Referral: The FDA Red Flags", Hearing Library, www.digicare.org, 2002.
