Lichen planus - Lichen Planus is a muco-cutaneous disease of immunological origin. It leads to a characteristic pruritic, papular, violaceous eruption of polygonal shape and is often covered with fine scales. Lichen planus most commonly leads to thick patchy rough, scaly skin that develops on the flexor surfaces of the upper extremities, around the ankles, in the genital region genitalia, and on the mucous membranes and is itchy in nature. It causes scarring alopecia leading permanent hair damage. Taenia capitis - It is a fungal dermatophyte infection of the scalp and hair caused especially by the Trichophyton and Microsporum. It causes contagious non-scarring alopecia. It causes inflammatory lesions such as pustules, scaling and itching. The hallmark of diagnosis is patches of hair loss with a "black-dot" pattern on examination. The clinical diagnosis is confirmed by mycological examination. Androgenic alopecia - It is an autosomal dominant disorder which is the most common cause of alopecia in both men and women. It causes miniaturisation of the hair follicles which is androgen dependent and caused by scalp dihydrotestosterone. There is a typical shoening of the hair cycle leading to increased numbers of anagen hairs entering the telogen phase and thus leading to premature hair fall. It leads to scarring alopecia. Alopecia areata - It is a inflammatory non-scarring alopecia of auto-immune origin. There is a inappropriate immune response due to the hair follicle associated antigens. The patient presents with well - demarcated patches of reversible hair loss. Histologically there is a typical peribulbar lymphocyte infiltration. The disturbance of hair shaft growth leads to characteristic exclamation point hairs which is the hallmark for diagnosis. Ref: Textbook of Cosmetic Dermatology By Robe Baran, 3rd Edition, Page 561; The Manual of Dermatology By Jennifer A. Cafardi, Page 15-64; Aging Hair By Ralph M. Trueb, Desmond J. Tobin, Pages 201-202; Evidence-Based Dermatology By Hywel Williams, Pages 386-387