Acute urticaria: It is a limited edematous reaction with dilated small blood vessels and increased permeability of the skin mucosa caused by a variety of etiologies. It is often an acute attack, with the sudden appearance of a pruritic erythematous rash all over the body, which can be accompanied by high fever, and in severe cases, chest tightness, dyspnea, decreased blood pressure, or even shock, which can heal naturally within 1 to 2 weeks and should be treated actively. Chronic urticaria: It is a constant occurrence of wind-like lesions that lasts for more than two months or several years, and the severity of the disease and its onset can vary greatly from person to person. The main symptom is severe itching of the skin, and the appearance of different sizes and shapes of wind masses. They can be round, oval, isolated, scattered or fused into patches. When the puffs are large, they can be pale white, with prominent pores on the surface, resembling orange peel. In severe cases, there may be anaphylactic shock-like symptoms such as panic, irritability, nausea, vomiting, and even lowered blood pressure. Some patients may have abdominal pain, diarrhea, or even choking. The duration of chronic urticaria can last from several months to several years, or even decades. Cholinergic urticaria: The symptoms of urticaria appear after exposure to heat. When the body temperature increases after exercise, sweating, hot room, hot bath, heat, hot food or drink, nervousness, excitement, etc., the blood flow stimulates the thermoregulatory center of the brain, which excites the cholinergic nerves and releases acetylcholine, and it is because the body is allergic to acetylcholine, a chemical, that we call this allergy-induced symptom cholinergic urticaria. The symptoms of cholinergic urticaria are characterized by: 1. a general feeling of stinging and itching on the skin. 2. 2. Usually appear after heat (hot drinks, hot baths), emotional excitement and exercise. After stopping exercise or calming down, the symptoms can subside. Most often occurs in youth. 3, often in the trunk and the proximal skin of the limbs (except axillary, palm and plantar) appear red, about 2 mm wind mass, this wind mass quickly come and go without leaving traces. Severe cases may be accompanied by gastrointestinal symptoms, such as abdominal pain and diarrhea. Cold urticaria: Cold urticaria is a special type of winter urticaria, which is an allergic reaction caused by human exposure to cold environment. In addition, there is a familial cold urticaria, which often occurs in infancy and can be seen as early as 1 week after birth. Patients develop a rash in half to four hours of exposure to cold, without itching, and the rash is erythematous and windy, accompanied by systemic symptoms such as fever, chills, arthralgia, and headache. Papular urticaria: It is a pruritic skin disease that occurs in children. The lesions are often round or poke-shaped rubella-like lesions with pinhead to small rice-sized blisters at the tip, scattered or in clusters, or larger blisters. They occur on the extensor surfaces of the limbs, trunk and buttocks. The lesions usually fade on their own after a few days to a week, leaving temporary hyperpigmentation. The lesions may also appear in batches and last for a period of time. The itching is intense and can cause pyoderma due to repeated scratching. The etiology of this disease is complex, most believe that insect bites, such as fleas, lice, mites, midges, bedbugs and mosquitoes. Skin Scratching: Also known as artificial urticaria. After scratching or scratching the skin with a blunt instrument, striated elevations occur along the scratches, accompanied by itching, and soon subside. It can occur alone or in combination with urticaria. It can occur at any age. It lasts for months or years and often has no apparent cause.