Hypersensitivity Reactions and Allergy questions

These flashcards cover the key concepts and facts about hypersensitivity reactions, types of allergies, and their mechanisms.

What are hypersensitivity reactions?

Immunological reactions resulting in excessive 'overreaction' following secondary exposure to an antigen.

How many types of hypersensitivity reactions are there?

Four types exist: Type I, Type II, Type III, and Type IV.

What is an example of Type I hypersensitivity?

Classic allergic reactions such as hay fever and asthma.

What role do genetic factors play in allergies?

About 75% of children with two atopic parents will also be atopic.

What is the Hygiene Hypothesis?

Proposes that declining family size and reduced exposure to germs lead to increased allergy rates.

What are the essential molecular stages of the allergic response?

IgE production in response to an initial exposure, binding to mast cells and basophils, followed by cross-linking upon secondary exposure.

What mediators are released during degranulation in allergic reactions?

Preformed mediators like histamine and stored precursors such as prostaglandins and leukotrienes.

What occurs during an anaphylactic shock?

Life-threatening sudden circulatory and respiratory failure due to massive release of mast cell mediators.

What is Type II hypersensitivity?

Cytotoxic reactions mediated by IgG and IgM that lead to the destruction of target cells.

What blood type is termed the universal donor?

Type O, due to the absence of red cell antigens.

What causes erythroblastosis fetalis?

An Rh- mother becomes sensitized to Rh+ antigens from her Rh+ baby during pregnancy.

What does Type III hypersensitivity involve?

Immune complex reactions mediated by IgA, IgG, or IgM, leading to tissue damage if not cleared.

What is a major feature of Type IV hypersensitivity?

Delayed reactions mediated by T cells, often referred to as contact dermatitis.

What is the common contact allergen in females?

Nickel, which can cause reactions in up to 25% of females aged 14 and older.

What are some treatment options for allergic reactions?

Non-sedating antihistamines, bronchodilators, and corticosteroids.

Why is skin testing used to diagnose allergies?

It visualizes reactions to allergens by observing wheal and flare responses.

What preventive measure can be taken against chronic exposure reactions?

Avoiding known allergens and practicing good hygiene.