The body is always sudden itch for a while and disappear on its own, may be hives, allergies or eczema. 1. Hives: hot and cold stimuli, mosquito bites, etc. make the body undergo a hypersensitivity reaction, which increases vascular permeability and causes local vasodilatation. Because these chemicals will be cleared by the body very quickly, it will appear faster and disappear faster. 2. Allergy: skin contact with allergens lead to itching, redness and swelling of the skin, first of all, as far as possible to clarify the causes of skin allergies, common allergens such as dust, drugs, pollen. 3. Eczema: eczema is caused by a variety of internal and external factors of a class of inflammatory skin diseases, patients usually have itching, eczema in many parts of the body can appear. Peripheral peripheral neuritis and other diseases will also appear sudden itchy situation, the body is always a sudden itch for a while and disappear on their own, to the regular hospital dermatology consultation, diagnosis is clear and follow the doctor’s instructions for targeted treatment.