whitehead
Last reviewed 01/2018
This is seen in acne vulgaris.
In this condition the keratin plug has sealed off the pilosebaceous duct. The orifice of the pilosebaceous duct fails to dilate (in contrast to the formation of a blackhead) and the expanding plug ruptures the wall of the duct. This results in the release of the contents of the duct into the dermis where they excite an inflammatory reaction.