Rough skin on the arms, piece by piece, is usually associated with keratosis pilaris, neurodermatitis, lichen planus and other causes. 1. Keratosis pilaris: Keratosis pilaris, also known as keratosis pilaris, is a chronic follicular keratosis pilaris. It occurs on the upper arms and thighs, and is symmetrically distributed. The lesions are follicular papules of needle tip to grain size, and there is a special roughness in the affected area of the skin. 2. Neurodermatitis: neurodermatitis is a chronic inflammatory skin disease associated with genetic allergies, lesions manifested as skin thickening, infiltration, brownish red or light gray, hyperpigmentation, surface roughness, often accompanied by itching. 3. Lichen planus is an idiopathic inflammatory dermatosis, typical lesions for polygonal purple-red flat papules, preferably in the limbs flexion. Typical skin lesions are raised purplish-red flat papules, corn grain to mung bean size or larger, polygonal or rounded, clear boundary, wax-like film on the surface, visible white glossy dots or fine shallow white reticulate stripes, as the characteristic skin lesions. Roughness of the skin on the arm may be due to other reasons, it is recommended to go to the dermatology department of the hospital in a timely manner to clarify the cause of the disease, according to the doctor’s advice to give targeted treatment.