Skin Care State Board Theory Practice Test

At the skin level, a comedo is a blocked pore or hair follicle filled with sebum and keratin. This blockage creates the basic acne lesion by trapping oil and dead skin cells inside the pore. When the plug reaches the surface and darkens from oxidation, it’s an open comedo; when the plug stays beneath the surface, it’s a closed comedo. Milia are small keratin-filled cysts that occur in the epidermis and aren’t caused by blockage of a hair follicle, so they aren’t comedones. A pore is simply the opening of a follicle or duct, not the blockage itself. A sebaceous cyst is a true cyst with a lining and contents separate from a simple blocked pore, so it’s a different lesion.