A report on Allergen

SEM of miscellaneous plant pollens. Pollens are very common allergens.
The house dust mite, its feces and chitin are common allergens around the home
Common food allergens

Type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body.

- Allergen
SEM of miscellaneous plant pollens. Pollens are very common allergens.

26 related topics with Alpha

Overall

Hives are a common allergic symptom.

Allergy

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Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.

Hives are a common allergic symptom.
A summary diagram that explains how allergy develops
Tissues affected in allergic inflammation
Degranulation process in allergy. Second exposure to allergen. 1 – antigen; 2 – IgE antibody; 3 – FcεRI receptor; 4 – preformed mediators (histamine, proteases, chemokines, heparin); 5 – granules; 6 – mast cell; 7 – newly formed mediators (prostaglandins, leukotrienes, thromboxanes, PAF).
An allergy testing machine being operated in a diagnostic immunology lab
Skin testing on arm
Skin testing on back
Patch test
Anti-allergy immunotherapy

Common allergens include pollen and certain foods.

Pollen grains from a variety of plants, enlarged 500 times and about 0.4 mm wide

Allergic rhinitis

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Pollen grains from a variety of plants, enlarged 500 times and about 0.4 mm wide
Illustration depicting inflammation associated with allergic rhinitis
Patch test

Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air.

Angioedema of the face such that the boy cannot open his eyes. This reaction was caused by an allergen exposure.

Anaphylaxis

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Serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site.

Serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site.

Angioedema of the face such that the boy cannot open his eyes. This reaction was caused by an allergen exposure.
Signs and symptoms of anaphylaxis
Urticaria and flushing on the back of a person with anaphylaxis
Skin allergy testing being carried out on the right arm
Patch test
An old version of an EpiPen brand auto-injector

Diagnosis is based on the presenting symptoms and signs after exposure to a potential allergen or irritant and in some cases, reaction to physical exercise.

Eczema—a typical atopic manifestation

Atopy

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Tendency to produce an exaggerated immunoglobulin E immune response to otherwise harmless substances in the environment.

Tendency to produce an exaggerated immunoglobulin E immune response to otherwise harmless substances in the environment.

Eczema—a typical atopic manifestation

Atopy may have a hereditary component, although contact with the allergen or irritant must occur before the hypersensitivity reaction can develop (characteristically after re-exposure).

The structure of the IgE antibody

Immunoglobulin E

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Type of antibody (or immunoglobulin (Ig) "isotype") that has been found only in mammals.

Type of antibody (or immunoglobulin (Ig) "isotype") that has been found only in mammals.

The structure of the IgE antibody
The role of mast cells in the development of allergy.
Degranulation processes 1: antigen; 2: IgE antibody; 3: FcεRI receptor; 4: preformed mediators (histamine, proteases, chemokines, heparin); 5: granules; 6: mast cell; 7: newly formed mediators (prostaglandins, leukotrienes, thromboxanes, PAF)

IgE that can specifically recognise an allergen (typically this is a protein, such as dust mite Der p 1, cat Fel d 1, grass or ragweed pollen, etc.) has a unique long-lived interaction with its high-affinity receptor FcεRI so that basophils and mast cells, capable of mediating inflammatory reactions, become "primed", ready to release chemicals like histamine, leukotrienes, and certain interleukins.

SEM of miscellaneous plant pollens: Pollens are very common allergens.

Type I hypersensitivity

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SEM of miscellaneous plant pollens: Pollens are very common allergens.

Type I hypersensitivity (or immediate hypersensitivity) is an allergic reaction provoked by re-exposure to a specific type of antigen referred to as an allergen.

An Alutard SQ injection kit

Allergen immunotherapy

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Medical treatment for environmental allergies, such as insect bites, and asthma.

Medical treatment for environmental allergies, such as insect bites, and asthma.

An Alutard SQ injection kit

Immunotherapy involves exposing people to larger and larger amounts of allergen in an attempt to change the immune system's response.

Patch test

Patch test

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Diagnostic method used to determine which specific substances cause allergic inflammation of a patient's skin.

Diagnostic method used to determine which specific substances cause allergic inflammation of a patient's skin.

Patch test
Weak positive
Strong positive

When skin is exposed to an allergen, the antigen-presenting cells (APCs) – also known as Langerhans cell or Dermal Dendritic Cell – phagocytize the substance, break it down to smaller components and present them on their surface bound major histocompatibility complex type two (MHC-II) molecules.

Illustration of allergic conjunctivitis

Allergic conjunctivitis

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Inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy.

Inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy.

Illustration of allergic conjunctivitis
Eye with mild allergic conjunctivitis

Although allergens differ among patients, the most common cause is hay fever.

Crystallographic structure of the Fel d 1 dimer, the primary allergen present in cat saliva

Fel d 1

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Secretoglobin protein complex that, in cats, is encoded by the CH1 and CH2 (chain 2/Fel d 1-B) genes.

Secretoglobin protein complex that, in cats, is encoded by the CH1 and CH2 (chain 2/Fel d 1-B) genes.

Crystallographic structure of the Fel d 1 dimer, the primary allergen present in cat saliva

It is the primary allergen present on cats and kittens.