When an unusual odor, often described as cheesy, emanates from the post-auricular fold—the crease directly behind the ear—it is a common, localized hygiene issue. This distinctive smell is the result of a concentrated mix of natural bodily secretions and the skin’s resident microorganisms. The area behind the ear is a hidden spot where these substances accumulate, creating a microenvironment conducive to odor production.
The Biological Mechanism of the Odor
The characteristic “cheesy” smell results from common skin bacteria metabolizing natural secretions behind the ear. This area is rich in eccrine sweat glands (producing water and salt) and sebaceous glands (secreting sebum, an oily mix of fats and waxes that lubricates the skin).
The odor is generated when bacteria, notably Staphylococcus and Corynebacterium, break down compounds in these secretions. These microorganisms break down amino acids in the sweat, such as leucine, into short-chain fatty acids, also known as volatile organic compounds (VOCs). One of these compounds is isovaleric acid, known for its strong, pungent, and cheesy aroma, which is also present in many types of strong cheese.
Common Causes of Buildup
The physical anatomy of the post-auricular fold naturally creates a sheltered, warm, and moist environment that encourages the accumulation of secretions and bacterial growth. Because the area lacks direct exposure to air and sunlight, sweat and oil are not easily evaporated or rubbed away. This creates a perfect incubator for the skin’s resident flora.
External factors also contribute to buildup by trapping moisture and debris against the skin. Physical obstructions like glasses, sunglasses, hearing aids, or headbands press against the fold, blocking airflow and concentrating material. Residue from hair products, such as shampoos or hairspray, can migrate to the area and mix with natural oils and dead skin cells. This sticky mixture forms a buildup that provides a constant food source for the odor-producing bacteria.
Immediate Solutions and Hygiene Practices
The most effective solution involves consistent and thorough hygiene, starting with a simple, mild soap or cleanser. During bathing, specifically wash the entire area behind the ears, using your fingers or a soft washcloth to gently rub the skin. Ensure the soapy water makes contact with the crease, rather than relying on runoff from washing your hair.
After washing, meticulous drying of the post-auricular fold is essential for prevention. Since bacteria and yeast thrive in moisture, gently patting the area completely dry with a clean towel or using a cool setting on a hairdryer inhibits microbial growth. People who wear glasses or hearing aids should also regularly clean the frames or devices that contact the skin. If the odor is accompanied by a persistent rash, pain, swelling, or thick discharge, it may indicate a skin condition like seborrheic dermatitis or a localized infection, requiring professional medical attention.