When people think about rare physical traits, they often picture something dramatic or immediately noticeable. Yet some of the most unusual features are surprisingly subtle. One example is a tiny hole or small dimple near the upper part of the ear. This little mark, often mistaken for a scar or old piercing, is actually something known as a preauricular sinus.

A preauricular sinus, sometimes called a preauricular pit or fistula, is a small congenital opening present from birth. It forms during early fetal development, around the sixth week of pregnancy, while the ear’s structures are taking shape. If certain tissues fail to fuse completely, a narrow tract or tiny pit remains.

This trait is often hereditary and can run in families. It may appear on one ear or both, though having it on both sides is less common. Because it is usually painless and barely visible, many people live their entire lives without realizing they have it.

For most individuals, the sinus causes no health problems and does not affect hearing. However, the small opening can sometimes trap bacteria. When that happens, the area may become infected, leading to redness, swelling, tenderness, or discharge.

Infections are typically treated with antibiotics and basic care, such as warm compresses and keeping the area clean. If infections occur repeatedly, doctors may recommend a simple surgical procedure to remove the tract entirely, preventing future issues.

Beyond medical concerns, the feature is interesting from a developmental standpoint. Some researchers, including Neil Shubin, have suggested it might reflect ancient evolutionary traits, though this idea remains theoretical. Ultimately, the preauricular sinus is a harmless variation that highlights the subtle uniqueness of human biology.