Hi, this is Tom, and in this episode I'm going to be going through Allergy.

And you can find notes at 0.0.5.com and in the 0 to Finals Pediatrics book.

And you can find flashcards and questions at members.0.0.0.com.

So let's jump straight in.

Allergy refers to immune system hypersensitivity to allergens. Allergens are proteins that the immune system recognizes as foreign and

potentially harmful, leading to an allergic immune response.

Allergens are types of antigens.

Antigens are proteins that can be recognized by the immune system.

The body will come into contact with millions of different antigens,

and very few of them will lead to a hypersensitivity reaction.

Allergens are antigens, but not all antigens are allergens.

A to P describes a genetic tendency to develop IGE, or immunoglobulin-E, mediated allergic diseases, such as eczema, hay fever, allergic rhinitis,

food allergies, and allergic asthma. These conditions are referred to as atopic conditions.

Let's talk about the different types of hypersensitivity reactions.

The Coombs and Gel classification is used to categorize hypersensitivity reactions,

from type 1 to type 4. Type 1 hypersensitivity reactions involve IGE antibodies to specific allergens, which triggers mass cells and basophils to release histamines and other cytokines that cause inflammation.

This causes an immediate reaction.

Examples are food allergies, insect sting allergy, anaphylaxis and allergic rhinitis.

Type 2 hypersensitivity reactions involve IgG and IgM antibodies binding to antigens and activating the complement system, causing cell damage.

Examples are hemolytic disease of the newborn and blood transfusion reactions.

Type 3 hypersensitivity reactions involve the accumulation of immune complexes that damage local tissues.

Examples are systemic lupus erythematosis or SLE and post-streptoccal glomerulinephritis.

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