The common causes of dark and rough skin on the back include acanthosis nigricans, chronic eczema and neurodermatitis. 1. Acanthosis nigricans: this disease mainly occurs in the neck, armpits and other parts of the body, and in severe cases, it can involve the whole waist and even the back. Its main manifestations are velvety thickening, obvious dryness and roughness of the whole skin, and deepening of the local skin color at the lesions, etc. Malignant acanthosis nigricans can also occur. Malignant acanthosis nigricans will also have the symptom of itching. 2. Chronic eczema: repeated episodes of this chronic inflammation can lead to keratosis and hypertrophy of the skin, with the prolongation of the course of the disease, there will also be lesions of epidermal roughness and deepening of pigmentation, and some people deepening of pigmentation, which may lead to black skin. 3. Neurodermatitis: also known as chronic lichen simplex, its onset and psychoneurological factors are closely related to the neck, back, waist, etc., the main symptoms for intense itching and accompanied by papules fused into the mossy lesions, the affected area of the skin is usually dry, hypertrophic. Due to the intense itching, patients keep scratching will appear hyperpigmentation, which will lead to localized skin blackening. Therefore, if the skin on the back is dark and rough, and there are other uncomfortable symptoms, it is recommended to consult a doctor in time to clarify the diagnosis and symptomatic treatment.