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allergic reaction, defined as sensitivity beyond what is considered normal

First Encounter

The first time an antigen (allergen) is encountered, the body becomes "sensitized" or forms antibodies, but no visible signs of hypersensitivity is exhibited.

Second encounter

1.) the allergen is encountered by mast cells and basophils, each coated with a particular group of antibodies that wsere formed during the first encounter
2.) then, chemicals such as histamine are released
3.) The severity of the reaction depends upon where in/on the body the chemicals are released

Tendency of allergies being inherited

at least one in five people have had or will have allergies related to hay fever (most common allergy)

Four principle types of hypersensitivities

Anaphylaxis reactions, cytotoxic reactions, immune complex reactions, cell mediated reactions,

anaphylaxis reaction

occurs within a few minutes after a sensitized person is re-exposed to a particular antigen, certain chemical agents are released, which hekp to attract neutrophils and eosinophils to the area.


increases permeability and dilation of blood capillaries, resulting in edema, erythema (redness) increase mucus csecretion, and smooth muscle contractions.


slow-reacting substances that tend to cause prolonged contractions of certain smooth muscles ( asthma attacks)


affects smooth muscle of the respiratory system and can cause an increase in mucus secretion

Localized anaphylaxis

symptoms usually depend upon the route in which antigens enters the body,

upper res. system type 1

itchy and tearing eyes, congested nasal passageways, coughing and sneezing,

Lower res system type 1

asthma-like symptoms, wheezing and shortness of breath caused by constriction of smooth muscles in the bronchial tubes

Gastrointestinal tract type 1

certain food allergies can cause diarrhea, however, other factors are usually involved, some hives or may even lead to systemic shock.

Food related allergies type 1

eight foods are responsible for 97% of the food related allergies, eggs, peanuts, other types of nuts, milk, soy, fish, wheat, peas, etc.

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