Inexplicable itchy arms can be considered related to neurodermatitis, pruritus in old age or other systemic diseases (such as viral hepatitis) and other diseases. 1. Neurodermatitis: it can appear under stress, anxiety or change of living environment, etc., there is intermittent itching in the elbow, limbs and other parts of the body, you can see the appearance of the rash, and later appear localized mossy changes, the skin will be hypertrophic, deepening of the skin lines. 2. Pruritus: such as pruritus in old age, dry and atrophic skin or sex hormones and other endocrine functions related to hypogonadism, can be itchy in all parts of the body; cold winter, the climate is dry, can also cause winter pruritus, often in the undressing of the bed, self-sensation of itchy forearms, legs and other places. 3. Viral hepatitis: after infection with hepatitis virus, in the acute stage, due to liver cell damage, jaundice can occur, skin and mucous membranes are light yellow to dark yellow, which can be accompanied by mild itching of the skin. If frequent itching of the skin occurs, you can consult a doctor in time, after clarifying the cause of the disease, under the guidance of the doctor for the cause of the symptomatic treatment.