What are benign, keratin-filled cysts that can appear just under the epidermis without a visible opening called?

The correct term for benign, keratin-filled cysts that appear just under the epidermis without a visible opening is milia. Milia are small, white bumps that are most commonly found on the face, especially around the eyes, and are often mistaken for whiteheads. They develop when keratin becomes trapped beneath the surface of the skin, leading to the formation of these tiny cysts.

Milia differ from other skin conditions in that they do not have an opening and are typically not inflamed or filled with pus, which distinguishes them from pustules. Pustules are inflamed lesions filled with pus and are often associated with acne, while general cysts can refer to many types of fluid-filled sacs and do not specifically describe this particular form of keratin-filled cyst. Vesicles, on the other hand, are small blisters that contain clear fluid on the surface of the skin. These terms help clarify the unique characteristics of milia compared to other dermatological issues.