Slide 1
An allergen is usually harmless but can trigger an immune reaction
An allergy is an immune reaction to a substance that is usually harmless. The triggering substance is called an allergen.
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Pollen, foods and other materials can enter through different routes. A reaction is shaped by the person’s immune response as well as the material, so ordinary exposure does not affect everyone alike.
Slide 2
Sensitization can leave IgE attached to mast cells
In many immediate allergies, the immune system makes immunoglobulin E (IgE) antibodies against an allergen. These antibodies can attach to mast cells.
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This preparation can occur before a noticeable later reaction. Sensitization is therefore not the same event as the release of mediators that produces symptoms on a subsequent encounter.
Slide 3
A later encounter can release histamine and other signals
When the allergen engages attached IgE, mast cells can release histamine and other substances. These signals alter nearby tissues.
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Histamine can increase vessel permeability and influence nerves and smooth muscle. One released mediator can therefore contribute to several effects rather than producing a single universal symptom.
Slide 4
Location helps determine the reaction’s effects
A response in the nose differs from one affecting skin or airways. Allergic reactions range in extent and severity.
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A severe systemic reaction is called anaphylaxis. This term describes a potentially life-threatening pattern, not merely an unusually irritating local allergy.
Slide 5
Similar symptoms do not automatically mean allergy
Not every unpleasant response to a food or exposure is an allergy. Immune mechanisms must be distinguished from other forms of intolerance.
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Clinical assessment combines the history with appropriate tests. A laboratory sign of sensitization alone does not establish that every symptom after an exposure was caused by that allergen.
Sources
- Histamine: The Stuff Allergies are Made of
MedlinePlus, NIH
- Allergic reactions
MedlinePlus Medical Encyclopedia