There are many possible causes of hearing loss. These can be divided into two basic types, called conductive and sensorineural hearing loss. A third type is called mixed hearing loss and can be a combination of the other two types.
	conductive hearing loss
	is caused by anything that interferes with the transmission of sound from the outer to the inner ear. Possible causes include:

		Middle ear infections (otitis media)
		Collection of fluid in the middle ear ("glue ear" in children)
		Blockage of the outer ear (by wax)
		Damage to the eardrum by infection or an injury
		Damage to the bones (ossicles) of the middle ear due to injury
		Otosclerosis, a condition in which the ossicles of the middle ear become immobile because of growth of the surrounding bone
		Rarely, rheumatoid arthritis affects the joints between the ossicles

	sensorineural hearing loss
	is due to damage to the hair cells in the inner ear and/or to the pathway for sound impulses from the hair cells to the auditory nerve and the brain. Possible causes include:

		Age-related hearing loss - the decline in hearing that many people experience as they get older
		Acoustic trauma (injury caused by loud noise) to the hair cells
		Head trauma
		Viral infections of the inner ear (may be caused by viruses such as mumps or measles)
		Ménière's disease, which involves abnormal pressure in the inner ear
		Certain drugs, such as high doses of aspirin, quinine and some rarely used antibiotics, which can affect the hair cells
		Acoustic neuroma, a benign (non-cancerous) tumour affecting the auditory nerve
		Viral infections of the auditory nerve such as mumps and rubella
		Infections or inflammation of the brain or brain covering, e.g. meningitis
		Multiple sclerosis
		Brain tumour
		Stroke
		Other conditions such as diabetes, untreated high blood pressure, thyroid problems and many more.

	Hearing loss can be congenital or acquired. A congenital hearing loss is when the hearing loss occurs before or just after birth. Exposure to certain diseases in utero or soon after birth can harm the hearing mechanism of a baby. Acquired hearing loss happens at a later stage and can be due to factors such as disease, noise or trauma to the head.

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