Allergic reactions

Allergen - an antigen that causes an allergic response

Anaphylaxis - a severe allergic reaction that can cause death

Mast cells - present in most tissues and produce histamine

Immunoglobulin E - a type of antibody produced in an allergic response

Type-I hypersensitivity is an immediate response to an allergen

This is a reaction, often an overreaction, to an antigen that would otherwise be harmless

Any antigen that causes this kind of response is an allergen

Typically, allergens include pollen, fur, dust, foods including peanuts, and latex

Dilation of blood vessels (vasodilation)

Increased permeability to immune cells and molecules

Decreases blood pressure

Contracts smooth muscle lining the airways, making breathing more difficult

Activation of fluid-secreting cells (runny nose and eyes) to expel the allergen

Antihistamines bind to the gap between two antibodies on the mast cell, stopping histamine from doing the sam

Cortisone can be used to suppress the immune response in general

If the reaction is severe (anaphylaxis) an adrenaline shot is needed to constrict the blood vessels (decrease swelling), relax airway muscles, and increase the heartbeat to prevent cardiac damage

Desensitisation - receive small doses of allergen to produce IgG antibodies (involved in humoral response). If IgG react to allergen before IgE binds to it, the allergic response is avoided. Patient receives larger doses over time, and becomes less sensitive. Also called allergen immunotherapy.