What are milia?

Milia are small, keratin-filled cysts that typically form beneath the outer layer of the skin, which is the epidermis. These cysts often appear as tiny white or yellowish bumps and can occur on various parts of the face, particularly around the eyes and cheeks. The buildup of keratin, a fibrous protein found in skin, hair, and nails, is what leads to the formation of these cysts, and they are often mistaken for whiteheads but are fundamentally different in their structure and development.

In contrast, the other options describe different skin conditions or issues. Inflamed cysts would relate more to conditions like acne or sebaceous cysts, which involve inflammation and are not specifically characterized by keratin. Bacterial infections in hair follicles pertain to conditions like folliculitis, which is caused by bacterial invasion and is not related to milia. Dark spots from sun exposure refer to hyperpigmentation or sun spots, which result from increased melanin production due to UV exposure and do not involve keratin-filled structures. Thus, the correct identification of milia as keratin-filled cysts highlights their unique pathophysiology compared to these other dermatological conditions.