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- Dictionaryhypersensitive/ˌhʌɪpəˈsɛnsɪtɪv/
adjective
- 1. having extreme physical sensitivity to particular substances or conditions.
- 2. easily hurt, worried, or offended: "proximity to death makes people hypersensitive and aware"
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The meaning of HYPERSENSITIVE is excessively or abnormally sensitive. How to use hypersensitive in a sentence.
Hypersensitivity (also called hypersensitivity reaction or intolerance) is an abnormal physiological condition in which there is an undesirable and adverse immune response to an antigen. It is an abnormality in the immune system that causes immune diseases including allergies and autoimmunity.
Hypersensitive means too easily upset by criticism or very easily influenced, changed, or damaged by a physical activity or effect. Learn more about the word, its synonyms, and how to use it in sentences with Cambridge Dictionary.
- Overview
- Definition
- Type 1 hypersensitivity reaction
- Type 2 hypersensitivity reaction
- Type 3 hypersensitivity reaction
- Type 4 hypersensitivity reaction
- Nonallergy hypersensitivity reaction
- Summary
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A hypersensitivity reaction happens when the immune system mistakenly identifies harmless substances as harmful. There are several types of hypersensitivity reactions, depending on the class of substance that triggers it.
An antigen or allergen can refer to a toxic or foreign substance that causes an immune reaction. After detecting an antigen and perceiving it as a potential threat, the immune system mounts an immune response to dispose of it.
The body can produce different types of hypersensitivity reactions, depending on the antigen a person has exposure to and how the body responds to it.
This article discusses the different types of hypersensitivity reactions.
A hypersensitivity reaction is an extreme or unnecessary immune response that the body has to an antigen.
There are four different types of hypersensitivity reactions. Some evidence suggests a potential fifth type, but this may actually be a subset of type 2 hypersensitivity reactions.
Each type of hypersensitivity reaction is an extreme immune response to an antigen. Each type of reaction differs based on the type of antigen the body identifies, what type of immune response the body generates, and how quickly the body produces the response.
Some people may refer to hypersensitivity reactions as allergies, as these are a form of hypersensitivity. Although people use these terms interchangeably, an allergic reaction typically refers to the signs and symptoms a person may experience, while a hypersensitivity reaction describes the immunological process that occurs in the body.
Type 1 hypersensitivity causes an immediate response and occurs after a person has exposure to an antigen. With this type of reaction, the body responds to an antigen by producing a specific type of antibody called IgE.
There are different components that can trigger type 1 hypersensitivity responses, including antigens that come from:
•food products, such as nuts, shellfish, and soy
•animal sources, such as cats, rats, or bee stings
•environmental sources, such as mold, latex, and dust
•allergic conditions, such as allergic rhinitis, allergic asthma, and conjunctivitis
Similar to type 1, type 2 hypersensitivity reactions also involve antibodies. In fact, type 2 and type 3 hypersensitivity both result from the same class of antibody, called IgG. The difference between them lies in the form of antigens that generate a response. Additionally, type 2 can also involve IgM antibodies.
Type 2 hypersensitivity causes cytotoxic reactions, meaning that healthy cells die as they respond to the antigens. This can cause long-term damage to cells and tissues, resulting in conditions such as:
•the blood disorder immune thrombocytopenia if there are not enough platelets
•autoimmune hemolytic anemia if the red blood cells burst
•autoimmune neutropenia if the body destroys neutrophils
•autoimmune conditions such as Graves’ disease
In type 3 hypersensitivity, antigens and antibodies form complexes in the skin, blood vessels, joints, and kidney tissues. These complexes cause a series of reactions that lead to tissue damage.
Causes of a type 3 hypersensitivity reaction can include:
•drugs that contain proteins from different organisms, such as antivenins
•the drug infliximab, which people use to manage autoimmune conditions
•animal sources, such as insect stings or tick bites
Type 3 hypersensitivity reactions can lead to:
Unlike the other types, type 4 hypersensitivity reactions are cell-mediated.
Instead of antibodies, white blood cells called T cells control type 4 hypersensitivity reactions. Experts can further subdivide these reactions into type 4a, type 4b, type 4c, and type 4d based on the type of T cell involved and the reaction it produces.
This type also differs from the other three in that it causes a delayed reaction.
The three subsets of type 4 hypersensitivity are as follows:
•contact dermatitis
•tuberculin-type hypersensitivity
Although hypersensitivity reactions are allergic reactions, some people may experience a non-immune anaphylactic reaction to certain drugs or foods. Some people may call this a nonallergic drug hypersensitivity reaction or refer to it as a pseudoallergic, idiosyncratic, or anaphylactoid reaction.
These reactions are often hard to distinguish from allergic reactions, but they noticeably cause symptoms directly, without the release of antibodies or T cells.
A hypersensitivity reaction occurs when the body produces an unnecessary and undesirable immune response following exposure to a certain antigen.
Many people refer to hypersensitivity as a form of allergy. Most research suggests that there are four types of hypersensitivity reactions, but some evidence suggests that there may also be a fifth type.
Different classes of antibodies moderate types 1, 2, and 3. Experts consider these types immediate hypersensitivity reactions because they occur within 24 hours of exposure to the antigen.
T cells moderate type 4 reactions, and specialists consider this type a delayed hypersensitivity reaction because it usually occurs 48–72 hours after exposure.
Less is known about type 5, but it may be similar to — or a subset of — type 2.
Diagnosis and treatment vary according to the type of hypersensitivity reaction a person experiences and the symptoms and conditions that result from the reaction. With each situation, it is important to identify and remove the cause of the hypersensitivity reaction to minimize further harm.
Hypersensitivity reactions are extreme or unnecessary immune responses to harmless substances. Learn about the four types of hypersensitivity reactions, how they differ, and how to diagnose and treat them.
- Helen Millar
very easily changed or damaged by physical conditions, or easily upset: He’s hypersensitive about his height.
Hypersensitive definition: excessively sensitive. See examples of HYPERSENSITIVE used in a sentence.
Hypersensitivity is a condition in which the immune system reacts in an extreme way to a substance in the body. Learn more about the types, causes and effects of hypersensitivity from Cambridge Dictionary, with examples and translations.
