allergic reactions


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allergic reactions

acute inflammatory skin hypersensitivity reaction (redness, tissue oedema, pruritus) induced by the histamine released from local mast cells in response to allergen contact in susceptible individuals (Table 1)
Table 1: Classification of types of hypersensitivity reactions
Type IType IIType IIIType IVType V
AntigenPollens, moulds, mites, drugs, foods, parasitesCell surface moietiesBacteria, fungi, parasitesCell or tissue moietiesCell surface receptors
MediatorsIgE and mast cellsIgG, IgM, complementIgG, IgM, IgA, complementT-cell-activated macrophages and lymphokinesIgG
TestsSkin tests (wheal and flare)Coombs' test
Red cell agglutination
Antibody precipitation
Immune complexesSkin test (erythema, induration)Indirect immunofluorescence
Time to reaction5-10 minutes6-36 hours4-12 hours48-72 hoursVariable
HistologyOedema, vasodilatation, mast cell deregulation, eosinophilsTarget cell damageAcute inflammation, neutrophils, vasculitisPerivascular inflammation, mononuclear cells, granuloma, caseation and necrosis in TBNormal or hypertrophy
Characteristic diseasesExtrinsic asthma, atopic eczema, allergic rhinitis, anaphylaxisHaemolytic anaemia, transfusion reactions, HDN, Goodpasture's syndrome, addisonian pernicious anaemia, myasthenia gravisAutoimmune disease (RA, SLE, glomerulonephritis)
Low-grade persistent infection (viral hepatitis)
Environmental diseases (farmer's lung)
Pulmonary TB, contact dermatitis, graft-versus-host disease, insect bites, Hansen's diseaseGraves, disease, myasthenia gravis
TreatmentAntigen avoidance
Topical corticosteroids
Sodium cromoglicate
Exchange transfusion, plasmapheresis, immunosuppressivesCorticosteroids, immunosuppressives, plasmapheresisImmunosuppressives, cortico-steroids, antigen removalTreatment of presenting disease

Ig, immunoglobulin; TB, tuberculosis; HDN, haemolytic disease of the newborn; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus.

hypersensitivity

An excessive reaction, local or systemic, or inappropriate immune response to an antigen. Four types of immune responses are usually described, but the main reaction involving the eyes is type 1. They are also called allergic reactions types 1-4.
type 1 hypersensitivity An immediate, abnormal reaction occurring when an antigen reacts with an antibody (e.g. immunoglobulin E (IgE)) attached to a mast cell or basophil. This leads to the release of specific chemical mediators of allergy (e.g. histamine) that react with target organs throughout the body. Systemic signs include: itching, lacrimation, skin rash and possibly haemodynamic collapse and shock. Allergic conjunctivitis is an example of this type of hypersensitivity.
Type 2 h . (cytotoxic h.) is caused by an interaction of antibody and antigens on cell surfaces. Examples: Graves' disease, myasthenia gravis. Type 3 h. (immune-complex mediated h.) is mediated by a combination of antigen-antibody. Example: systemic lupus erythematosus. Type 4 h. (T cell-mediated h.) is a delayed reaction (several days to develop) mediated by T lymphocytes. Example: rheumatoid arthritis. See antihistamine; mast cell stabilizers.
References in periodicals archive ?
Camp Guide to Managing Severe Allergic Reactions (Includes basic information about anaphylaxis, including food and insect sting allergy.
Based on what the scientific community currently knows about molds, it's far easier in court to establish that mold spores have caused an allergic reaction than to show they have triggered a neurological response, said William F.
Improved Food Labeling Needed to Reduce Allergic Reactions," (press release); Milwaukee: American Academy of Allergy, Asthma & Immunology, Sept.
Myth: Each allergic reaction to food become increasingly worse.
Food inspectors are calling on members of the public not to eat the product if they are prone to allergic reactions.
The allergic reaction may be to a drug such as penicillin, an insect sting, or even some foods.
In polluted areas, children are twice as apt to have allergic reactions as adults are.
Nitrile Exam Gloves: These are the protein-free disposable gloves, which are utilized with the aim of abating allergic reactions.
Auvi-Q (epinephrine injection, USP) is the first-and-only epinephrine auto-injector with audio and visual cues for the emergency treatment of life-threatening allergic reactions in people who are at risk for or have a history of anaphylaxis.
Common allergic reactions include hives, skin rashes, flushing and warmth of the skin, bronchospasm or shortness of breath, especially in those with asthma," Health Scout quoted Dr.
A hundred years ago, people would likely have been shocked that modern humans are plagued with illnesses that range from annoying to deadly due to allergic reactions.
The patient developed allergic reactions to foods, and she started experiencing cough, wheezing, and shortness of breath when exposed to even low-levels of irritant chemicals.