Clinical relevance of hair microscopy in alopecia

Summary Hair microscopy can clarify the cause of hair loss in a range of diagnoses. Most of these are associated with hair breakage, the rest are related to lack of growth. Hair breakage may be due to excessive trauma or underlying susceptibility, where structural clues may be present. Lack of growth reflects follicular dynamics and represents the central mechanism of most common causes of alopecia. In such conditions, microscopy only reveals nonspecific confirmation of short anagen. Although this may assist clinical diagnosis, microscopy in alopecia only allows exclusion of diagnoses related to hair breakage. Confidence in the outcome of hair microscopy is based on the size of the sample of hairs, the length of the hair, the characteristics of the observations and the experience of the person undertaking the microscopy.