What distinguishes a whitehead from a blackhead?

The correct distinction between a whitehead and a blackhead lies in their classification as comedones, which are types of acne lesions formed by clogged pores. A whitehead is indeed classified as a closed comedo, meaning that the clogged pore is sealed off from the air. This results in a small, elevated bump on the skin, which appears white or flesh-colored because the contents of the pore are not exposed to oxygen. Conversely, a blackhead is an open comedo, where the clogged pore remains open to the air. This exposure causes the material inside to oxidize and turn black, giving it its characteristic appearance.

Understanding this difference is important in dermatology and skincare, as the treatment and management of these two types of acne lesions can differ significantly based on their nature.

The other provided options do not accurately describe the characteristics or classifications of whiteheads and blackheads. For instance, describing whiteheads as blisters or cysts misrepresents their structure, while suggesting that one is flat and the other elevated does not hold true for these specific types of lesions. Likewise, categorizing them as types of lacerations and fissures completely misaligns with their true nature as comedonal acne lesions.