What is the cause of serum sickness urticaria

Serum sickness urticaria is skin wheals caused by drug allergies and other reasons. It is also a common manifestation of urticaria. After the onset of the disease, patients are prone to some skin manifestations, as well as fever, joint pain and other symptoms. Severe symptoms can have an adverse effect on the patient's cardiovascular health and renal function.

1. Causes

Currently, the serum preparations that cause serum sickness in clinical practice mainly include tetanus antitoxin, diphtheria antitoxin, various snake venom antitoxins, and antilymphocyte globulin (ATG); the drugs that cause serum sickness mainly include macromolecular drugs such as penicillin, streptomycin, sulfonamides, salicylates, butazone, phenytoin sodium, and dextran.

About 1% to 3% of blood recipients develop systemic urticaria after blood transfusion. It is currently believed that this is caused by the formation of immune complexes, which cause changes in blood vessels and smooth muscles, and may also indirectly lead to the release of mediators from mast cells through allergic toxins.

About 15% to 20% of multiple blood recipients have anti-IgA IgG antibodies in their blood, which can combine with IgA in the blood of the donor to form immune complexes, activate complement and cause urticaria and angioedema.

In some cases, no antibodies are found, and urticaria may also occur after the infusion of immunoglobulin G. The reason is that after the transfusion of immunoglobulin G, the concentration of immunoglobulin G in the blood increases, causing them to coagulate and fix complement.

2. Pathogenesis

It is a typical type III hypersensitivity reaction. The body can produce antibodies against the antigenic components of foreign serum that enter the body or against antigenic complex proteins formed by the combination of certain drugs that act as haptens and proteins in the body. When the amount of antibodies formed is slightly less than the antigens that have not disappeared in the body, immune complexes can be formed that are deposited on the blood vessel walls, thereby activating the complement system, generating vasoactive substances, neutrophil chemotactic factors, etc., causing local congestion and edema.