Itching is a sensation that causes a person to have the desire to scratch. Itchy skin is not the name of a disease, but a symptom, and it is the most common symptom of a skin condition. Many diseases can have itchy skin manifestations. The diseases that can be classified as itchy skin can be simply divided into 2 main categories, one is skin diseases without rash manifestations and the other is skin diseases with rash manifestations. No rash manifestation, that is, no skin abnormalities, only itching, this disease is called pruritus, the common causes are dry skin, systemic diseases (such as diabetes, liver disease, kidney disease, tumors, etc.), psychosomatic diseases. Skin diseases with rash manifestations, the rash can manifest as red patches, papules, patches, blisters, etc. There are quite a lot of pruritic skin diseases with rash manifestations, the most common ones are allergic skin diseases, such as urticaria, contact dermatitis, insect bite dermatitis, eczema, etc.; fungal infectious skin diseases, such as ringworm, ringworm, ringworm, etc.; viral skin diseases, such as chickenpox and herpes zoster, the rash of chickenpox is usually asymptomatic and can also manifest as pruritus, the most common symptom of herpes zoster is pain, but patients with milder conditions can also The most common symptom of herpes zoster is pain, but patients with milder disease can also be pruritic; bacterial infectious dermatoses, which are mostly red, swollen, and hot, while impetigo can be pruritic; erythematous scaling dermatoses, such as psoriasis; vascular dermatoses, which are mostly asymptomatic or painful, but a few can also be pruritic, such as allergic vasculitis and pigmented purpura dermatoses; skin tumors, such as keloids and cutaneous T-lymphocytoma.