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Chapter: 08. Allergy
Immunity vs. Allergy
Entity
Definition & Concept
Primary Function or Response
Common Triggers / Causes
Immunity (Immune System)
• The ability of the body to defend against infections and develop resistance to infectious diseases.
• Defends the body from foreign bodies and pathogens to maintain health.
• Microorganisms (viruses and bacteria)• Foreign proteins• Toxic substances
Allergy
• An exaggerated or abnormal reaction (hyperactivity) of the immune system to certain foreign substances that are harmless to most people.
• Triggers hypersensitive inflammatory symptoms or diseases due to an overactive immune response.
• Allergens (pollen, dust, animal fur, food items, etc.)
Period of Allergy: Seasonal vs. Perennial Allergy
Entity
Occurrence & Period
Common Triggers
Examples & Sub-types
Seasonal Allergy
• Develops only during specific seasons.• Comes and goes with the season.
• Pollen grains (from grasses, trees, and weeds)• Ragweed• Moulds• Dust mites
• Spring Allergies• Summer Allergies• Fall Allergies• Winter Allergies• Hay Fever (allergic rhinitis)
Perennial Allergy
• Appears at any time year-round.
• Indoor dust• Mould• Cockroaches• Feathers• Pet dander• Specific food items• Insect bites
• Indoor allergies• Food allergies• Insect-bite allergies
Entry Routes of Allergens
Entry Route
Method of Entry
Common Allergens
Nose
• Through breathing
• Pollen• Mould spores• Dust particles• Dust mites• Perfumes
Mouth
• By eating
• Food items (soya, wheat, milk, peanuts, nuts, eggs, fish, shellfish)• Medicines
Skin
• By contact
• Sap / latex from certain plants• Mites• Strong sunlight• Cosmetics• Insect bites• Injections
Types of Allergies Based on Causative Agents
Type of Allergy
Primary Causative Agents
Common Symptoms
Key Examples Mentioned
Respiratory Allergies
• Seasonal air-borne allergens
• Sneezing, coughing, runny nose, itchy/watery eyes, wheezing, breathing difficulties
• Hay fever (allergic rhinitis)• Allergic asthma
Food Allergies
• Specific proteins/substances in food items
• Stomach upset, immediate wheezing, vomiting, skin rashes, anaphylaxis (in severe cases)
• Milk allergy (casein protein)• Wheat allergy• Nut allergy (peanuts, walnuts, cashews)• Egg, fish, shellfish, soy, and mushroom allergies
Skin Allergies
• Contact with external irritants, saps, or stings
• Red and itchy rashes, swollen pale-red bumps or patches
• Contact dermatitis• Urticaria (hives)• Poisonous plant sap allergy (ivy, oak)• Insect stings (wasps, bees, fire ants)
Other Allergies
• UV radiation, specific cosmetic ingredients, metals, or drugs
• Skin irritation, dry eyes, conjunctivitis, nausea, diarrhoea, urticaria, low blood pressure
• Sun allergy• Cosmetic allergy (fragrance, preservatives)• Metal allergy (nickel, gold)• Eye allergies• Drug allergy (aspirin, penicillin, sulpha drugs)
Expressions of Severe Allergic Reactions
Allergic Reaction
Primary Physical Symptoms
Severity & Danger Level
Underlying Physiological Feature
Hay Fever
• Swollen, reddened, and watery eyes• Running nose, sneezing, coughing, and headache
• Mild to moderate; standard seasonal/perennial respiratory reaction
• Triggered by pollen grains
Allergic Asthma
• Narrowing of bronchi, bronchospasm• Sneezing, difficulty in breathing, wheezing, and breathlessness
• High; most common form of allergy
• Affects the airways and respiratory system
Anaphylaxis
• Skin-wide rashes, swollen face and lips• Puffy eyes, thick-feeling throat (swollen tissues)• Arterial dilation, low blood pressure, shortness of breath
• Critical; sudden and most dangerous reaction; can lead to sudden death
• Anaphylactic shock produced by the discharge of large quantities of histamine from mast cells
Diagnostic Tests for Allergies
Diagnostic Test
Alternative Name
Procedure / Methodology
What It Measures & Identifies
Skin-prick Test
• Prick testing• Puncture testing
• Small amounts of suspended allergens/extracts are injected intradermally into the patient’s skin (forearm or back) using a syringe.• Each site is marked and numbered.
• Detects inflammatory reactions (swelling and redness) to identify specific triggering allergens.
Blood Test
• Not mentioned in text
• Blood sample is taken from the patient to perform laboratory analysis.
• Measures the concentration of specific IgE antibodies in the blood to predict the type and severity risk of allergy.
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