Cerumen, or "earwax," is a mixture of hydrophobic secretions from modified apocrine sweat glands in the outer 1/3 of the auditory canal and desquamated epithelium from the auditory canal. Cerumen protects the auditory canal from infection by maintaining a hydrophobic environment within the canal and by serving as a barrier to foreign body entry into the canal. In the normal ear, cerumen is secreted into the auditory canal and then gradually migrates towards the external auditory meatus and outside of the auditory canal, carrying with it dust and debris which might cause irritation to the external ear.

Cerumen impaction occurs when cerumen is not cleared from the auditory canal. It is defined as cerumen buildup causing symptoms or preventing a clinically indicated otoscopic examination. Note that this clinical definition is met by either patient symptoms or provider difficulty in visualizing the ear during otoscopic examination. Further note that physical impaction is not necessary to meet the definition of cerumen impaction. Symptoms of cerumen impaction commonly include hearing loss or difficulty, auditory canal itching or pain, tinnitus, and coughing (recall that the vagus nerve supplies some sensory innervation to the external ear and also innervates the upper airway; this explains this symptom).

Cerumen impaction may also cause impaired clearance of debris from the auditory canal and can form microenvironments that may foster microbial growth. Otitis externa may result if cerumen impaction is not managed appropriately. However, auditory canal inflammation may cause increased cerumen production. Therefore, in patients with recurrent otitis externa, it is recommended that specialist consultation be obtained. Additionally, patients with dermatologic diseases of the auditory canal may exhibit increased cerumen production but should be seen by specialists for disease-specific diagnostic and therapeutic workups. Finally, the group of patients who have had previous surgery or radiation therapy of the external ear should be seen by specialists rather than having cerumen impaction treated in the primary care setting. This is especially important to monitor for post-treatment complications or disease recurrence.

Cerumen impaction is estimated to affect 2%-6% of the population at any given time and up to 65% of nursing home residents. It is therefore an important diagnosis to be aware of and treat in the primary care setting.