There are two causes of itchy skin: 1. pruritus, mostly caused by dry skin, when attention should be paid to avoid excessive cleaning, such as soap, hot water and other irritants. 2. consider atopic dermatitis or urticaria, both of which are allergic diseases, mostly due to the body’s exposure to external allergens, such as food, drugs, various substances in the air, items around contact, etc. The combination of antibody and antigen will form an antigen-antibody conjugate, which will cause a series of inflammatory reactions such as rashes. The rash may appear as redness all over the body and it may feel itchy everywhere. You can recall whether you have been exposed to allergens from your diet, medication, and environment.