Non-Invasive Techniques for Evaluating Alopecia Areata

Alopecia areata (AA) is a disease affecting mostly young patients, being the second most prevalent cause of alopecia. For the assessment of AA patients, numerous non-invasive techniques are available. For diagnosing and treating AA, non-invasive hair follicle exploration is crucial. Trichoscopy, videodermoscopy, pull test, global scalp photography and scalp imaging techniques (reflectance confocal microscopy (RCM), multiphoton microscopy (MPM), and high-frequency ultrasonography (HF-USG) are non-invasive methods used to assess the hair loss. Short vellus hairs and yellow dots were the most commonly reported and sensitive trichoscopy signs of AA. Additionally, it was observed that AA activity was associated with black dots, micro-exclamation mark hairs and tapering hairs. A good prognosis of AA includes the transformation of vellus into terminal hairs. Reflectance confocal microscopy is a non-invasive imaging technique for in vivo evaluation of the skin and observation of cell morphology with a nearly histological resolution, which is helpful in diagnosis and management of AA. Additionally, MPM delivers information on hair follicles and scalp inflammation and can be utilized to assess hair growth while undergoing treatment. High-frequency ultrasonography allows distinguishing between hair cycle phases, which is undoubtedly important from the prognostic of AA. The current review aims to discuss the non-invasive methods of diagnosis of AA.