hypersensitivity reaction


Also found in: Dictionary, Thesaurus, Legal, Financial, Encyclopedia, Wikipedia.
Related to hypersensitivity reaction: delayed hypersensitivity reaction

hypersensitivity

 [hi″per-sen″sĭ-tiv´ĭ-te]
a state of altered reactivity in which the body reacts with an exaggerated immune response to a foreign agent; anaphylaxis and allergy are forms of hypersensitivity. The hypersensitivity states and resulting hypersensitivity reactions are usually subclassified by the Gell and Coombs classification. adj., adj hypersen´sitive.
contact hypersensitivity that produced by contact of the skin with a chemical substance having the properties of an antigen or hapten.
delayed hypersensitivity (DH) (delayed type hypersensitivity (DTH)) the type of hypersensitivity exemplified by the tuberculin reaction, which (as opposed to immediate hypersensitivity) takes 12 to 48 hours to develop and which can be transferred by lymphocytes but not by serum. Delayed hypersensitivity can be induced by most viral infections, many bacterial infections, all mycotic infections, and a few protozoal infections (leishmaniasis and toxoplasmosis). The scope of the term is sometimes expanded to cover all aspects of cell-mediated immunity including contact dermatitis, granulomatous reactions, and allograft rejection.
immediate hypersensitivity antibody-mediated hypersensitivity occurring within minutes when a sensitized individual is exposed to antigen; clinical manifestations include systemic anaphylaxis and atopic allergy (allergic rhinitis, asthma, dermatitis, urticaria, and angioedema). The first exposure to the antigen induces the production of IgE antibodies (cytotropic antibodies, reagin) that bind to receptors on mast cells and basophils. Subsequent exposure to the antigen triggers production and release of a diverse array of mediators of hypersensitivity that act on other cells producing symptoms such as bronchospasm, edema, mucous secretion, and inflammation.
hypersensitivity reaction the exaggerated or inappropriate immune response occurring in hypersensitivity, in response to a substance either foreign or perceived as foreign and resulting in local or general tissue damage. Such reactions are usually classified as types I–IV on the basis of the Gell and Coombs classification.

al·ler·gic re·ac·tion

a local or general reaction of an organism following contact with a specific allergen to which it has been previously exposed and sensitized; immunologic mechanisms gives rise to inflammation or tissue damage. Allergic reactions are classified into four major types: type I, anaphylactic and IgE dependent; type II, cytotoxic; type III, immune-complex mediated; type IV, cell mediated (delayed).

hypersensitivity reaction

an inappropriate and excessive response of the immune system to a sensitizing antigen, called an allergen. Several factors determine the degree of the response: the person's genetic predisposition for an exaggerated response, the amount of allergen, the kind of allergen, its route of entrance into the body, the timing of the exposures to the allergen, and the site of the allergen-immune mediator reaction. Hypersensitivity reactions are classified into four types according to the components of the immune system involved in their mediation. A type I or immediate hypersensitivity reaction occurs rapidly, within several minutes, on reexposure to an antigen, and is the result of interaction of immunoglobulin E and the antigen; anaphylaxis is a particularly severe type I hypersensitivity reaction. A type II or cytotoxic hypersensitivity reaction is one of tissue or cell damage resulting from antibody-antigen interactions on cell surfaces. A type III or immune complex-mediated hypersensitivity reaction is a local or general inflammatory response caused by formation of circulating antigen-antibody complexes and their disposition in tissues. A type IV hypersensitivity reaction (also called cell-mediated or T-cell-mediated hypersensitivity reaction) is one initiated by antigen-specific T lymphocytes. Unlike hypersensitivity reactions mediated by antibodies, this type takes one or more days to develop, and the hypersensitivity can be transferred by lymphocytes but not by serum. The term is often equated with delayed hypersensitivity reactions that are cytokine-mediated (as contrasted with direct cytolysis).
enlarge picture
enlarge picture
enlarge picture
enlarge picture
Hypersensitivity reactions

al·ler·gic re·ac·tion

(ă-lĕr'jik rē-ak'shŭn)
Local or general reaction of an organism after contact with a specific allergen to which it has been previously exposed and sensitized.
Synonym(s): hypersensitivity reaction.

Patient discussion about hypersensitivity reaction

Q. ALLERGIES what are they,who gets them,are they caused by pollen and food?

A. Allergy is the exaggerated and out-of-place reaction of the immune system to external substances or stimuli that are not harmful to the body, so the reaction actually damages the body instead of helping it.

The may be pollen and foods, as well as insect stings, drugs and almost any other substances.

You may read more here:
www.nlm.nih.gov/medlineplus/allergy.html
http://www.mayoclinic.com/health/allergy/AA99999

Q. what is the most common allergy? is it dust allergy?

A. thanks, I've heard of a new allergy treatment and trying to learn some more about the different kinds...

Q. what are the symptoms of Allergy?

A. from you question i understand that you think you might developed an allergy. so here is a web page with couple of videos explaining about allergies:
http://www.healthline.com/video/allergies

More discussions about hypersensitivity reaction
References in periodicals archive ?
This is a life-threatening situation especially for the patients who have latex hypersensitivity reaction.
Hypersensitivity reactions may be milder and more localised, and may also be chronic (eg hay fever and asthma).
P<0,05; ** - P<0,01; *** - P<0,001 Figure 1: Immediate hypersensitivity reaction to Candida allergen on different stages of HIV Immediate hypersensitivity reaction to Candida in HIV AIDS patients I stage 27,0% II stage 33,3% III stage 83,3% Note: Table made from pie chart.
Macrophage are responsive to a number of lymphokines that induce their growth differentiation and activation; since lymphokines are released by primed lymphocytes, produced chiefly by T-lymphocytes, on contact with an antigen [21], and the demonstration of a lymphookine mediated reaction in this study strongly supported the existence of T like lymphocytes in Tilapias and that the fish is capable of delayed hypersensitivity reactions.
Unusual clinical presentation of hypersensitivity reaction to abacavir.
8) Most patients will improve with antigen avoidance, which is more suggestive of a hypersensitivity reaction than an infection--particularly when symptoms resolve without antibiotics or antifungals.
HP is an inflammatory interstitial lung disease that results from a hypersensitivity reaction to the repeated inhalation of specific antigens found in a wide array of organic material and dust.
An observational study (it does not give any drugs) is recruiting 40 White and 40 African American patients 18 and older who have had a suspected hypersensitivity reaction to abacavir.
This is called a hypersensitivity reaction Having a family member with the condition increases your risk.
Allergic reactions to latex consist of immediate-type hypersensitivity reaction and delayed-type hypersensitivity reaction.
After extravasation of the intravenous hirudin site, the patient developed a delayed hypersensitivity reaction that histologically showed an epithelioid granulomatous infiltrate.
Patients should be aware that a hypersensitivity reaction can occur upon restarting abacavir.