There are "mosquito bags" in many parts of the body, and the itching is unbearable. Is it because the overwintering mosquitoes have started to "do things"? In fact, this situation is very likely to be urticaria. Well, why did you get a bag? Today, the doctor will take you to understand this "itchy" disease. Take you to know the "big family" of urticaria urticaria is a very common skin disease that can occur at any age. About 30% of people have urticaria at least once in their lifetime, which can be seen at any age and sex. According to the duration of illness, urticaria can be divided into acute urticaria and chronic urticaria. The symptoms of chronic urticaria last for more than 6 weeks. According to the etiology, urticaria can also be divided into spontaneous urticaria and induced urticaria. Among them, induced urticaria includes skin scratch, cold urticaria, delayed pressure urticaria, water source urticaria, sunlight urticaria, vibration vascular edema and contact urticaria. How did these "mosquito bags" come out? The etiology of urticaria is very complex. It can be divided into exogenous and endogenous according to different sources. Exogenous factors are mostly transient, while endogenous factors are mostly persistent. Exogenous factors: direct sunlight, skin friction and pressure, cold and hot stimulation, eating certain food or medicine, inhaling allergens, etc. Endogenous factors: bacterial and viral infection, fatigue, mental tension and chronic diseases. In addition to the factors listed above, there are other causes of urticaria. In general, the causes of acute urticaria are easy to find, while the causes of chronic urticaria are more difficult to determine. According to the current study, the symptoms of chronic urticaria in adults or children are rarely caused by allergy, but spontaneous. Mast cells in human body are the most important effector cells causing urticaria. They are widely distributed around the microvessels under the skin and visceral mucosa, and have strong immune regulatory functions. Although the name is mast cell, it has nothing to do with obesity. Mast cells in patients with urticaria can be activated by different mechanisms, releasing histamine, tryptase, interleukin, leukotriene and other substances, leading to wind mass, edema and itching symptoms. One of the important mechanisms is an immunoglobulin IgE in the human body, which plays a central role in the pathogenesis of urticaria. IgE can activate mast cells in different ways, and then release the above-mentioned histamine and other inflammatory mediators, leading to urticaria symptoms. When these symptoms appear, seek medical attention as soon as possible. Urticaria is mainly characterized by wind masses with different sizes and pruritus. The shape and size of the wind mass are variable, the center is raised, and the periphery is often accompanied by a red halo. It usually subsides within 24 hours, but it often appears in other areas of the body in turn. Most patients with chronic urticaria have a course of several years, even as long as 50 years. However, urticaria cannot be equated with fengtuan painting. Some patients with urticaria may also have vascular edema, mainly manifested as sudden swelling of dermis or subcutaneous tissue, accompanied by itching, pain and burning sensation (such as eyelids and lips). Compared with wind mass, the duration of vascular edema is longer, up to 72 hours. In addition to wind mass and angioedema, severe urticaria