1. ALLERGYALLERGY (TYPE 1 HYPERSENSITIVITY REACTION) 1

2. CONTENTS Definition of allergy. Definition of allergy. What and where are allergens?? What and where are allergens?? How does allergy develops?? How does allergy develops?? Mechanism of allergic reaction. Mechanism of allergic reaction. Which areas of the body may be affected? Which areas of the body may be affected? Who is at risk of allergies? Who is at risk of allergies? Different types of allergic conditions. Different types of allergic conditions. Diagnosis. Diagnosis. Treating allergic reactions. Treating allergic reactions. 2

3. DEFINITION OF ALLERGY Allergy involves an exaggerated response of the immune system, often to common substances such as foods, furry animal dander or pollen. The response is exaggerated because these foreign substances are normally seen as harmless by the immune system in nonallergic individuals. 3

4. ALLERGENS. induces allergic reactions in living organisms. foreign to the body. inhaled, ingested (eaten or swallowed), applied to the skin, or injected into the body. the symptoms and conditions that result depend largely on the route of entry and the type of allergen. 4

5. WHERE ARE ALLERGENS?? In the air we breathe: 1.Pollens from trees, grasses, and/or weeds 2.Dust mites 3.Animal proteins, including dander, skin, and/or urine 4.Mold spores 5.Insect parts, especially from cockroaches. 5

6. In what we ingest: 1.Foods: The most common food allergens are cow's milk, eggs, peanuts, tree nuts, wheat, soy,shellfish, finned fish. 2.Medications: Although any medication can cause an allergic reaction, common examples include antibiotics and anti- inflammatory agents, such as aspirin and ibuprofen. 6

7. .Touching our skin: cosmetics Poison ivy, sumac and oak Personal care products Nickel and other metals Latex 7

8. Injected into our bodies: 1.Insect venom. 2.Medications. 8

9. HOW DOES ALLERGY DEVELOP?? Encountering an allergen once is usually necessary to develop an allergy. ALLERGY developes only when a person is sensitized to a given allergen. Thus, there are two stages which develops an allergy: 1.Sensitisation 2.Re-exposure to allergen. 9

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11. - Re-exposure to allergen.It is possible for an individual to go their whole life carrying allergen-specific IgE bound mast cells without ever experiencing an allergic reaction or even being aware of the allergy..However, upon re-exposure to the offensive allergen, binding of the allergen to IgE on mast cells can initiate an aggressive and immediate immune response..In human, mast cells are found in the lungs, in the membranes of upper respiratory tract, in the skin and in the intestinal tract. Mast cells are rich in granules which contain histamine and several other biologically active substances like bradykinin, prostaglandins, etc. 11

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13. MECHANISM OF ALLERGIC REACTION Allergic reaction is a type1 hypersensitivity reaction i.e., IgE mediated hypersensitivity reaction. IgE is an antibody that all of us have in small amounts. Allergic individuals, however, generally produce IgE in larger quantities. Allergic reactions are triggered when allergens crosslink preformed IgE bound high affinity Fc receptors on mast cells. Once activated, mast cells are degranulated within few seconds, releasing a variety of mediators. The mediators can be classified as primary and secondary. -The primary mediators (example : histamines, heparin ) are produced before degranulation and are stored in granules. -The secondary mediators ( example : prostaglandins, leukotrienes, various cytokines ) either are synthesised after target – cell activation or are released by the breakdown of membrane phospholipids during degranulation process. 13

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15. Which areas of the body may be affected? Nose, eyes, sinuses and throat Lungs and chest Stomach and bowel Skin 15

16. Who is at risk for allergies ?? Can develop at any age. Initial exposure or sensitization period may even begin before birth. Family history, or genetics, plays a large role, with a higher risk for allergies if parents or siblings have allergies. Children born via Cesarean section have a higher risk of allergy as compared to children who are delivered vaginally. Exposure to tobacco smoke and air pollution increases the risk of allergy. More common in westernized countries. Timing of exposures to antigens, use of antibiotics also contribute to the development of allergies. 16

17. DIFFERENT TYPES OF ALLERGIC CONDITIONS: Allergic rhinitis (hay fever)- -refers to nasal symptoms that are due to aeroallergens. - Year-round, or perennial, allergic rhinitis is usually caused by indoor allergens, such as dust mites, animal dander, or molds. -Seasonal allergic rhinitis is typically caused by tree, grass, or weed pollens. - SYMPTOMS:.Runny nose.Stuffy nose.Sneezing.Itchy nose, ears, and throat.Postnasal drip (throat clearing).Watery exudation of conjuctivae. 17

18. Asthma- -Asthma is a respiratory condition that results from inflammation and hyper-reactivity of the airways, leading to recurrent, reversible narrowing of the airways. -Asthma can often coexist with allergic rhinitis. -Allergic asthma :airborne or blood-borne allergens, such as pollens,dust, fumes, viral antigens ; trigger an asthmatic attack. -Intrinsic asthma : in this case, an asthmatic attack can be induced by exercise or cold, apparently independently of allergen stimulation. -SYMPTOMS:. Shortness of breath.Wheezing.Coughing.Chest tightness 18

19. Allergic eyes (conjunctivitis)- -are inflammation of the tissue layers (membranes) that cover the surface of the eyeball and the under surface of the eyelid. -SYMPTOMS:.Redness under the lids and of the eye overall.Watery, itchy eyes.Swelling of the membranes 19

20. . ECZEMA (ATOPIC DERMATITIS): -commonly found in infants. - tends to occur in individuals at risk for other allergic conditions (asthma and allergic rhinitis) but is not usually caused by direct allergen exposure. -SYMPTOMS:.Dry skin associated with significant itching..Rashes occur..Involvement of the face, the front of elbows, and behind knees, though the rash can occur anywhere..Allergic individuals develop skin eruptions that are erythematous (rednesss of skin) and filled with pus. 20

21. Anaphylaxis- -It is a potentially life-threatening allergic reaction that can affect a number of organs at the same time. - Allergens that typically lead to anaphylaxis are foods, medications, and venom (bee stings). -SYMPTOMS:.Hives itching,present in 80%-90% of cases..Nasal congestion, runny nose, itchy eyes..Swelling of the tongue and/or throat..Abdominal discomfort, nausea, vomiting, diarrhea..Shortness of breath, wheezing, coughing..Low blood pressure, leading to lightheadedness, passing out, or shock. 21

22. DIAGNOSIS OF ALLERGY The doctor will ask the patient questions regarding symptoms, when they occur, how often, and what seems to cause them..Below are some examples of tests in order to diagnose allergies: 1.Blood test: This measures the level of IgE antibodies released by the immune system. This test is sometimes called the radioallergosorbent test (RAST) 2.Skin prick test: This is also known as puncture testing or prick testing. The skin is pricked with a small amount of a possible allergen. If the skin reacts and becomes itchy, red and swollen; it may mean an allergy is present. 3.Patch test: A patch test can identify eczema. Special metal discs with very small amounts of a suspected allergen are taped onto the individual's back. The doctor checks for a skin reaction 48 hours later, and then again after a couple of days. 22

23. TREATING ALLERGIC REACTIONS Antihistamines, corticosteroids, or decongestants. Use a saline sinus rinses. Use bronchodilators. Corticosteroid creams. Immunotherapy is a long-term treatment option for chronic allergy symptoms. Anaphylaxis is a medical emergency, and people should call 911 if they suspect someone is having an anaphylactic reaction. If the person carries an EpiPen, which is a self-injectable dose of epinephrine that is designed to treat anaphylaxis, inject this into their thigh, as soon as possible. 23

24. 24 Presented by : AREENA SALEEM 18MBM001 M.Sc. (Ag.) Microbiology Final year AMU Presented by : AREENA SALEEM 18MBM001 M.Sc. (Ag.) Microbiology Final year AMU