title: Alarm reaction of pilosebaceous apparatus.
abstract: A series of histologic changes involving the pilosebaceous structures are described under the term "alarm reaction." The follicular manifestation of this phenomenon is characterized by regression of hair matrix, forming a well-defined nest of small basaloid cells found in various parts of the follicular canal. The sebaceous glands either become undifferentiated, forming a solid mass of stratified squamous epithelium, or the sebaceous lobules are taken into the follicular canal and into the surface keratin layer.
mesh_terms: D000328:Adult; D005260:Female; D006197:Hair / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012627:Sebaceous Glands / Q000473:pathology*; D012871:Skin Diseases / Q000473:pathology*