Etiology and pathogenesis The etiology of this disease is unknown. It is similar to Mongolian spot, and is caused by melanocytes staying in the dermis as they migrate from the neural crest to the epidermis during embryonic development. The lesions of nevus of Ota are mostly distributed in the area of the first and second branches of the trigeminal nerve. Clinical manifestations Nevus of Ota is usually found in people of color, such as oriental and black people. About 2/3 of patients have nevus of ota at birth, while the rest appear between the ages of 10 and 20. The lesions are pale cyan, gray-blue, brown-blue to blue-black or yellow-brown patches or dense spots, with the edges of the patches often fading, and the spots are distributed in sharp clusters, varying in density, or with patches in the center and spots on the edges. Occasionally, small nodules similar to pigmented nevi can be seen in the pigmented spots, ranging from corn to green bean size. The color of the lesions is aggravated by sun exposure, exertion, menstruation, and pregnancy. The periorbital area, frontal area, forehead, zygomatic area, temporal area and nasal flank, and the area equivalent to the distribution of the first and second branches of the trigeminal nerve are commonly involved in this disease, with unilateral distribution and occasionally bilateral. The skin lesions may involve the scalp, auricle, neck, etc. The treatment of nevus of Ota is for cosmetic purposes, and the principle should be to remove the pigment without leaving scars or causing pigmentation or loss. At present, the commonly used lasers are 755nm emerald laser, 1064nm Nd:YAG laser, etc. The younger you are, the thinner your skin is, the more superficial your lesions are, the more vigorous your metabolism is, the stronger your absorption capacity is, and the number of treatments required is relatively small. Treatment should be carried out in stages, generally requiring 3-8 treatments, once every 3 months to 6 months. Generally speaking, the deeper the pigmentation of the lesion, the more treatment sessions are required, and eventually a complete treatment without scarring can be obtained. After the treatment, the wound surface should be kept clean and dry, and topical antibiotic ointment should be used to prevent infection, and the scab should fall off and heal in a week or so. The newborn skin is more red and tender, so care should be taken to avoid prolonged exposure to the sun and careful use of cosmetics.