Type III allergy is a so-called “immune complex type” reaction. In this case, antigen-antibody complexes are deposited in vessel walls of blood vessels and lead to local inflammation there, due to which the vessels can become narrowed and clogged and the affected organs can be destroyed.
What is type III allergy?
The classification of allergy types (including type III allergy) into four different categories is quite “old hat” in medicine: scientists Coombs and Gell published this classification in 1963, and since then it has been an integral part of medical studies and training in medical care professions. According to the current state of immunological research, the Coombs and Gell classification may actually be considered obsolete nowadays. Nevertheless, it is often used for didactic reasons and is suitable for understanding the pathophysiological processes behind the very diverse manifestations of allergic reactions. Serum sickness or intolerances to certain drugs such as penicillin belong to this category, and certain kidney and lung diseases or rheumatoid arthritis also have such an origin story.
Causes
The antigen-antibody reaction is actually a very useful part of our everyday immune defenses, helping the body to recognize invading bacteria and viruses on mucous membranes or in the bloodstream, mark them, and “throw them to the grub” of our own phagocytes. In many autoimmune diseases, this reaction is directed against the wrong antigens: It is no longer bacteria that are recognized, but components of the patient’s own blood or cell surfaces. Soluble antigen-antibody complexes are then deposited in vessel walls and tissue and trigger inflammatory reactions. These can become so bad that the affected organs are damaged as a result.
Symptoms, complaints, and signs
Signs of a type III allergy are noticeable within a few hours. Vascular inflammation usually develops. Red hemorrhages in a round shape refer to the disease. Mostly arteries and veins are affected. In addition to local signs, symptoms can also be noticed all over the body. In type III allergy, leukocytes release enzymes that damage the tissue. As a result, ulcers may appear and individual skin areas may die. Inflammation of the blood vessels is common, which experts call the Arthus reaction. Sometimes, with a time delay, the so-called serum sickness appears. The symptoms vary in intensity and are often mild. Thus, redness, itching and swelling remain. The symptoms subside on their own after some time. Inflammation of the kidneys or shock are the exception. Type III allergy often spreads to the entire body. Then the pathogens have settled in the bloodstream. Affected persons regularly complain of discomfort in the cardiovascular system. The heartbeat accelerates without any stress situation being present. Blood pressure plummets. Fever and diarrhea can accompany this condition. If renewed contact with the allergens occurs, this can promote a long-lasting illness.
Diagnosis and course
In the case of so-called serum sickness, this is a basically reasonable reaction. If a person is injected with certain proteins from the serum of other animal species, he or she usually does not tolerate them; they are recognized in the blood as foreign and marked by antibodies. Sometimes, however, medicine requires antiserum or vaccine serum, which can only be produced in animal species. This is purified and prepared by laboratory chemistry – nevertheless some bodies recognize it as foreign and fight against it. Then a type III allergy occurs. Antisera are used, for example, as protection against snake venom or as a passive vaccine to prevent infection with the hepatitis B virus if one has already had contact with it. Some people are also allergic to drugs such as penicillin in the sense of a type III reaction. Symptoms of this reaction include skin rash, fever, joint inflammation, kidney failure with edema, diarrhea. The type III reaction is also called a delayed type reaction because the symptoms do not appear until six to twelve hours after contact with the triggering antigen.Further examples of type III allergies lead deep into the pathology of autoimmune diseases: In panarteritis nodosa, there is inflammation of vessel walls throughout the body with vascular occlusion or internal bleeding. Characteristic autoantibodies can be detected here by laboratory chemistry. In immune complex glomerulonephritis, which can also be triggered by harmless respiratory infections, antigen-antibody complexes deposit in the tiny blood vessels of the kidney and block them. Anyone who suddenly notices swelling in the face or legs or a decrease in the amount of urine two to four weeks after a tonsillitis could be suffering from such an autoimmune phenomenon, which fortunately can often be treated well and in the short term. Rheumatoid arthritis, lupus erythematosus or exogenous allergic alveolitis, the latter also known as Farmer’s lung, are also type III reactions. In farmer’s lung, years of inhalation of farm-specific dusts, especially molds, results in antigen-antibody complex deposition in the lungs, leading to inflammation and subsequently to shortness of breath and hypertension in the pulmonary circulation. Analogously, there is also, for example, winemaker’s lung, woodworker’s lung, or cheese washer’s lung.
Complications
Type III allergy, along with type II allergy, is one of the allergy types with the highest risks for complications. Active uptake of immune complexes of allergens and IgG and IgM antibodies by granulocytes produces tissue-damaging enzymes that can lead to serum sickness, allergic vasculitis, or exogenous allergic alveolitis. Serum sickness occurs when antiserum or vaccine serum of animal origin is injected. This produces immune complexes that can be deposited in the joints and small blood vessels, causing inflammation. The disease, which is associated with fever, rash, joint pain and swelling of the lymph nodes, usually heals without consequences. In rare cases, however, severe courses with circulatory shock can occur. Allergic vasculitis is characterized by inflammation of small blood vessels. It can lead to various complications such as kidney failure, severe intestinal bleeding, mental disorders or strokes. In some cases, fatal courses occur. The prognosis depends on the severity and localization of the vasculitis. Exogenous allergic alveolitis can be treated very well. However, this is only true if the specific trigger is found. Otherwise, the course often becomes chronic. The lung tissue can then be remodeled in the course of pulmonary fibrosis, which leads to death in the long term. Furthermore, right heart strain is then also possible due to increased blood pressure in the small circulation, which in severe cases causes shortness of breath and heart failure.
When should you see a doctor?
Type III allergy always requires treatment by a physician. Since this disease cannot heal on its own, the affected person should always consult a doctor in the process. This is the only way to prevent further complications. Therefore, a doctor should be contacted already at the first symptoms and signs of this allergy. In the worst case, the disease can lead to the death of the affected person, if the internal organs are damaged. A doctor should be consulted for this disease if the affected person suffers from discomfort on the skin after ingesting a certain substance. There is severe redness or itching, which can spread over the entire body. It is not uncommon for Type III allergy to cause fever or severe diarrhea, which has a very negative effect on the quality of life of the affected person. If the symptoms are not treated, inflammation of the kidneys can also occur. As a rule, type III allergy can be diagnosed by a general practitioner or by an allergist. Further treatment usually requires a visit to a specialist.
Treatment and therapy
Given the range of these diseases, of course, each individual subtype of type III allergy has its own therapy. In the case of autoimmune diseases, in most cases the physician attempts to suppress the body’s immune system to the point where the formation of immune complexes diminishes and the inflammation of the vessel walls decreases. Medications such as cortisol or other immunosuppressants are used here.In the event of an allergic reaction, as in serum sickness, the only option is to immediately stop antigen delivery and provide symptomatic emergency therapy.
Prevention
For allergic lung diseases, the longer the contact with the triggering dusts, the more the disease progresses. Occupational safety measures are extremely important here for later health in the affected occupations.
Aftercare
Type III allergy requires comprehensive aftercare. After an allergic reaction, the physician should be consulted immediately. The initial examination serves to clarify the symptoms and to initiate therapy. The actual follow-up care begins as soon as the patient has recovered from the allergic reaction. First, the physician conducts a conversation with the patient to assess the severity of the allergy. The burden that the allergy has on the patient’s life is also important in choosing the aftercare treatment. The specialist can perform in-depth examinations and initiate hyposensitization, for example. Follow-up care for a type III allergy also includes specific immunotherapy. After an allergic reaction, measures should be taken to alleviate or completely eliminate the allergy. The primary care physician or allergist can put patients in touch with a specialty center where they can receive the necessary therapy. Follow-up care for a type III allergy is provided by the primary care physician or an allergist. Depending on the symptom picture and type of allergy, other specialists may be involved in treatment if needed.
What you can do yourself
Type III allergy can be treated by means of various self-help measures. First, it is important to avoid the triggering substances. Since this is not always possible in practice, a suitable emergency medication must also be available to quickly relieve the allergy symptoms in case of doubt. Basically, a healthy lifestyle should be led with a balanced diet and plenty of exercise. This keeps the immune system fit and enables it to counteract allergens more effectively. However, if an allergic reaction does occur, the emergency physician must be called or the patient must be taken to a hospital. Depending on the severity of the allergic reaction, rest or comprehensive medical treatment may be sufficient afterwards. Type III allergy is manifested by the fact that the allergic reaction occurs with a significant time delay after contact with the triggering substance. Therefore, affected individuals should closely monitor their diet and note any deviations with time and date. The data can then be used to identify the trigger. If complaints occur that indicate a mild allergic reaction, the allergy sufferer should drink plenty of fluids and take it easy for one or two days. If the discomfort does not subside on its own, a visit to the doctor is recommended.
