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Allergy and Hypersensitivity

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York University
Natural Science
NATS 1670
Motti Anafi

Allergy Monday, January 6,2014 • Allergic reactions are the evil part of the immune system. • Your immune system is usually working well if it is in some sort of balance between infection and immunity. • If infection is working stronger than immunity, this can result in an allergic reaction. • Allergies are abnormal sensitivities to antigens in the environment • Allergens are antigens that cause allergies • Allergens see ordinary substances as foreign, causing the immune system to overreact • 2 types of allergies: seasonal and chronic • Allergies are common in children, usually disappearing during teen years and re-appear in adulthood Dust mites • Dust mites can be found everywhere. They can cause allergic reactions in some people. Pollen • The allergic reaction of these takes place in a very unique time of the year. It is seasonal. Development of Allergic Reaction Typical allergic reaction First Type Tissue contact with allergen (antigen) à B cells produce IgE against allergen à IgE attaches to mast cells Sensitization: First exposure to allergen Second Type Allergens complex with IgE on mast cells à Mast cells release histamine and other chemical à Blood Vessels dialate and release plasma Reaction: Second exposure to allergen Mast Cells Resting Mast Cell Activated Mast Cell Mast cells and Basophils • Mast cells and basophils contain granules filled with inflammatory chemicals such as histamine • Sensitized cells bind IgE • They are able to release the potent inflammatory mediators • Degranulation • May be induced be aggregation of IgE bound to high-afinity receptors (Fc receptors on the surface of these cells • Specific antigen (allergen) is responsible for the IgE aggregation. Clinical Signs of Localized Allergic Reactions • The hypersensitivity reactions are usually mild and localized • Site of the reaction depends on the portal of entry • Inhaled allergens may cause hay fever, an upper respiratory tract response • Marked by watery nasal discharge, sneezing, itchy throat and eyes, and excessive tear production • Commonly caused by mold spores, pollens, flowering plants, some trees, and dust mites • Examples include pinkeye, Allergic rhinitis, nasal polyps, tonsillitis, etc. Asthma • Asthma is a result of genetics and environmental factors which make certain people more susceptible to allergens. • Disorder of the obstruction of breathing • Results in shortness of breath, wheezing (whistling sound) • There is a strong genetic component to asthma. However, it takes more than just genetics to have an attack. o Inhaled allergens  Causes inflammation  Induces bronchial smooth muscle to over secrete mucus and to contract • Most of the times, asthma is a result of inhaled allergens. Skin Allergies • Due to release of histamine and other mediators into nearby skin • Examples include eczema Food Allergies • An estimated 1.5 million Americans have peanut allergies • Peanut is the poster child of food allergies. • There chemicals in peanuts that can cause very severe reactions. • Vaccines against the flu contain traces of egg product, so if you are allergic to eggs, another alternative might be suitable Adverse Reaction to Food Find out about this^^ *Lactose intolerance has nothing to do with allergic reactions *10% of the world's population believes they have this unique allergic reaction, however, it is actually intolerance Food Allergies • Some foods may contain allergens o Cause diarrhea, vomiting and other gastrointestinal signs and symptoms o Can lead to an anaphylactic shock (people can be killed if they are not taken care of quickly enough) • Mainly (but not only) affect kids • Affects babies through breastfeeding Anaphylactic Shock • Degranulation of many mast cells at once causes the release of large amounts of histamine and inflammatory mediators • Can result in acute anaphylaxis or anaphylactic shock • Clinical signs o Bronchial smooth muscles contracts violently o Swelling of the larynx  Suffocation o Leakage of fluid from blood vessels  Drop in the blood pressure Treatment of Ana
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