Indentation on the skin

It is an allergic reaction of the skin and blood vessels. The formation of allergic reactions is caused by the internal and external causes. There is a special protein in the serum of such patients, which is immunoglobulin IgE. If such proteins are combined with allergens, the body will cause a series of reactions, and finally the mast cells around the skin blood vessels will release a large amount of histamine. Histamine will cause the skin blood vessels to dilate, and the serum will leak out of the blood vessels, and itching will occur. At this time, the skin scratch test is positive.