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What are the 4 types of hypersensitivity?

Hypersensitivity is an immune response that is exaggerated or excessive, leading to tissue damage as the immune response is directed to the body’s own cells and tissues. There are four types of hypersensitivity, each with its unique characteristics based on the immune response involved and the antigenic stimulus that triggers the response.

The first type of hypersensitivity is Type I, which is also known as immediate or allergic hypersensitivity. This type of hypersensitivity is characterized by the rapid onset of symptoms within seconds to minutes of exposure to an allergen, such as pollens, dust, or food. The response involves the release of immunoglobulin E (IgE), which binds to allergens and activates mast cells and basophils to release inflammatory mediators such as histamine, leukotrienes, and prostaglandins that cause vasodilation, edema, and smooth muscle contraction leading to symptoms like itching, hives, anaphylaxis, and asthma.

Type II hypersensitivity is also known as cytotoxic hypersensitivity, and it involves the activation of complement cascade and antibody-mediated cell toxicity targeting specific cells like red blood cells in hemolytic anemia or platelets in immune thrombocytopenia. The immune response is directed against antigens on the surface of the cells, leading to their destruction and organ damage.

Type III hypersensitivity is known as immune complex-mediated hypersensitivity, and it involves the formation of immune complexes in response to antigens, which deposit in tissues and trigger an inflammatory response that damages the tissues. The immune complexes are formed by the binding of antibodies to soluble antigens like DNA, drugs, or pathogens, leading to the activation of complement system and the recruitment of neutrophils that cause tissue damage.

Type IV hypersensitivity is a delayed-type hypersensitivity reaction that occurs 24-48 hours after exposure to the antigen. The response involves the activation of T cells that release cytokines, leukocytes, and chemokines, leading to the recruitment of macrophages and the destruction of the antigen.

This type of hypersensitivity is involved in cell-mediated immune responses against pathogens like mycobacteria, fungi or in allergic contact dermatitis caused by exposure to chemicals, metals or drugs.

Hypersensitivity reactions are pathological immune responses that can lead to tissue damage and organ dysfunction. The four types of hypersensitivity reactions include Type I, II, III, and IV, each with its unique mechanism and clinical presentation. Understanding the mechanisms of these hypersensitivity reactions is essential for diagnosing and treating the underlying conditions and preventing further complications.

What is IV hypersensitivity reaction?

IV hypersensitivity reaction, also known as intravenous hypersensitivity reaction, refers to a type of adverse reaction to intravenous medications that can cause a range of symptoms ranging from mild to severe, and in some rare cases, can even prove to be fatal. This reaction is caused by an immune system response to a particular medication or substance which has been introduced into the body through an intravenous route.

In many cases, the symptoms of IV hypersensitivity reaction can appear immediately or within the first few hours of receiving the medication. These symptoms can include a sudden drop in blood pressure or heart rate, shortness of breath, tightness in the chest, swelling, hives and skin rashes, fever, chills, tremors and seizures.

In rare instances, the symptoms can be life-threatening, leading to anaphylactic shock, a medical emergency that can cause the heart to stop beating, leading to death.

The factors that can contribute to IV hypersensitivity reaction include prior exposure to the medication in question or a cross-reacting substance, a history of allergies or asthma, and genetic predisposition. Certain medications and substances are more likely to cause IV hypersensitivity reactions than others.

Antibiotics, anti-inflammatory drugs, and contrast agents used for diagnostic imaging are known to cause such reactions.

The treatment of IV hypersensitivity reaction can vary depending on the severity of the symptoms. In mild cases, stopping the medication and administering antihistamines or corticosteroids can help alleviate the symptoms. In more severe cases, oxygen therapy and intravenous fluids may be needed. In life-threatening cases, immediate medical attention is required, and emergency measures such as epinephrine and cardiopulmonary resuscitation may be needed.

Iv hypersensitivity reaction is a serious and potentially life-threatening adverse reaction to intravenously administered medications. Healthcare providers administering medication through this route must be aware of the potential for such reactions and should always monitor their patients for any signs or symptoms of the same.

Early recognition and prompt treatment can help prevent serious complications and save lives.

What is the difference between Type 3 and 4 hypersensitivity?

Type 3 and Type 4 Hypersensitivity are two major types of autoimmune reactions observed in humans. While both types of hypersensitivity are based on immune responses against self-antigens, they differ significantly in their mechanisms and manifestations.

Type 3 Hypersensitivity is also known as immune complex-mediated hypersensitivity. The immune response in Type 3 Hypersensitivity is triggered when large immune complexes, formed due to the interaction of antigens with antibodies, fail to be removed by phagocytic cells. These immune complexes get deposited in various tissues and organs, leading to an inflammatory response.

The inflammatory response is caused by the activation of complement proteins, which attract and activate various immune cells such as neutrophils, macrophages, and eosinophils. The inflammatory response results in tissue damage and the release of various cytokines, which further exacerbate the immune response.

Examples of Type 3 Hypersensitivity include systemic lupus erythematosus, rheumatoid arthritis, and glomerulonephritis.

On the other hand, Type 4 Hypersensitivity is also known as delayed-type hypersensitivity. In Type 4 Hypersensitivity, the immune response is mediated by effector T-cells, primarily CD4+ Th1 cells or CD8+ cytotoxic T-cells. The effector T-cells recognize self-antigens presented by antigen-presenting cells (APCs) and trigger a delayed hypersensitivity reaction.

The reaction is characterized by the recruitment of inflammatory cells such as macrophages, neutrophils, and T-cells to the site of the reaction. The inflammatory response results in tissue damage at the site of the reaction. Examples of Type 4 Hypersensitivity include contact dermatitis, tuberculin skin test, and graft rejection.

Type 3 Hypersensitivity is mediated by immune complexes, while Type 4 Hypersensitivity is mediated by effector T-cells. Type 3 Hypersensitivity results in a systemic inflammatory response, while Type 4 Hypersensitivity results in tissue damage at the site of the reaction. Understanding the differences between these two types of hypersensitivity is crucial for the diagnosis and treatment of autoimmune and inflammatory diseases.

What are the 4 types allergic reactions?

Allergic reactions are caused by the immune system’s overreaction to a substance that it perceives as a threat. These substances are called allergens, and they can range from environmental triggers like pollen or dust mites to food allergens like peanuts or shellfish.

There are four types of allergic reactions, each with its own distinct symptoms and mechanisms of action.

Type 1 allergic reactions are also known as immediate hypersensitivity reactions. They are the most common type of allergic reaction and usually occur within seconds to minutes of exposure to an allergen. This type of reaction is triggered by the immunoglobulin E (IgE) antibody, which is produced by the immune system in response to allergens.

IgE antibodies then bind to a type of immune cell called mast cells, which release histamine and other inflammatory chemicals into the bloodstream, causing symptoms such as hives, itching, and swelling.

Type 2 allergic reactions are also known as cytotoxic reactions. They occur when the immune system produces antibodies that attack and destroy healthy cells in the body, mistaking them for foreign invaders. Examples of type 2 allergic reactions include autoimmune diseases like rheumatoid arthritis and lupus, which occur when the immune system attacks its own tissues.

Type 3 allergic reactions are also known as immune complex-mediated reactions. This type of reaction occurs when the immune system produces large amounts of antibodies in response to an allergen, forming immune complexes in the bloodstream. These immune complexes can then deposit in tissues throughout the body, causing inflammation and damage.

This type of reaction is often seen in autoimmune diseases like systemic lupus erythematosus and rheumatoid arthritis.

Type 4 allergic reactions are also known as delayed hypersensitivity reactions. They usually occur several hours to days after exposure to an allergen and are mediated by a type of immune cell called T cells. In this type of reaction, T cells mount an immune response against the allergen, leading to inflammation and tissue damage.

Type 4 allergic reactions are seen in many allergic skin conditions, including contact dermatitis and poison ivy rash.

Allergic reactions can manifest in different ways, but they all involve an overreaction of the immune system to an allergen. Understanding the different types of allergic reactions is essential in the diagnosis and management of allergies and can help healthcare providers develop effective treatment plans.

What is type 4 autoimmune disease?

Type 4 autoimmune disease is a condition that involves the body’s immune system attacking its own cells and tissues. This type of autoimmune disease is also known as cell-mediated or delayed-type hypersensitivity. Unlike other types of autoimmune diseases that involve antibodies targeting tissues and organs, type 4 autoimmune disease is driven by T cells that recognize and destroy cells that are identified as foreign or abnormal.

There are many different types of type 4 autoimmune diseases. Examples include psoriasis, multiple sclerosis, rheumatoid arthritis, and Crohn’s disease. These diseases can affect different parts of the body, including the skin, nervous system, joints, and gastrointestinal tract.

The causes of type 4 autoimmune disease are not fully understood, but it is believed that genetic factors, environmental triggers, and immune dysregulation may all play a role. Certain infections, exposure to toxins, and stress can also trigger the development of type 4 autoimmune diseases.

Symptoms of type 4 autoimmune disease vary depending on the particular disease, but can include inflammation, pain, fatigue, and organ dysfunction. Diagnosis of type 4 autoimmune disease usually involves blood tests to look for the presence of autoantibodies or inflammatory markers, as well as imaging tests and biopsies to assess tissue damage.

Treatment for type 4 autoimmune disease typically involves medications that suppress the immune system, such as corticosteroids, immunosuppressants, and biologic agents. Lifestyle modifications, such as stress reduction and a healthy diet, can also be helpful in managing symptoms.

Type 4 autoimmune disease is a complex and diverse group of conditions that involve T cell-mediated immune responses that lead to inflammation and tissue damage. It can affect various parts of the body, and treatment typically involves a combination of medications and lifestyle changes.


  1. Type IV Hypersensitivity Reaction – PubMed
  2. 4 Types of Hypersensitivity Reactions – ThoughtCo
  3. Hypersensitivity Reactions (Types I, II, III, IV)
  4. What are the different types of hypersensitivity reactions?
  5. How to Recognize the 4 Types of Hypersensitive Reactions