Exclamation mark hairs in Alopecia Areata

Exclamation mark hairs in AA

Exclamation mark hairs are 3-4 mm hairs that are wide at the top and thin at the bottom. They are seen in individuals who have recently developed a patch of alopecia areata. 

These hairs are caused by the inflammation around the hair bulb that impairs the ability of the hair matrix to make a proper hair.

 
Long standing alopecia areata does not have much  inflammation and correspondingly exclamation mark hairs are not seen.