1.0 Allergy: The Hypersensitive Response
An Allergy is an exaggerated or hypersensitive reaction of the immune system to certain foreign substances that are otherwise harmless to most people. While the immune system is designed to protect us from pathogens, in the case of an allergy, it misidentifies a common substance as a threat.
Allergen: The substance that triggers an allergic reaction (e.g., pollen, dust).
Allergy: The actual condition or the state of being hypersensitive.
Common Allergic Triggers
Allergens can enter the body through various routes:
- Airborne Allergens: Pollen, dust mites, mold spores, and pet dander.
- Food Allergens: Peanuts, milk, eggs, seafood, and soy.
- Contact Allergens: Latex, certain cosmetics, or chemicals in detergents.
- Injectable Allergens: Insect stings (bees/wasps) or certain medications like Penicillin.
Symptoms of Allergic Reactions
The symptoms depend on the point of entry and the severity of the reaction:
- Respiratory: Sneezing, runny nose, coughing, and wheezing (common in Hay Fever).
- Skin: Rashes, itching, redness, or hives (Urticaria).
- Digestive: Swelling of the lips/tongue, stomach cramps, or vomiting.
Entry Routes and Effects
| Route | Mechanism | Common Condition |
|---|---|---|
| Inhalation | Breathing in dust/pollen. | Asthma, Hay Fever. |
| Ingestion | Eating allergic foods. | Food Allergy. |
| Touch | Skin contact with substances. | Eczema, Dermatitis. |
When an allergen enters the body, the immune system produces antibodies (IgE). These antibodies trigger Mast Cells to release a chemical called Histamine. Histamine is responsible for most allergy symptoms, such as swelling, itching, and mucus production. This is why Antihistamines are used as treatment.
Anaphylaxis (or Anaphylactic Shock) is a severe, life-threatening allergic reaction that affects the whole body. It can cause a sudden drop in blood pressure and severe difficulty in breathing. It requires immediate medical attention, usually an injection of Epinephrine (Adrenaline).
2.0 Diagnosis & Management of Allergies
Because the symptoms of an allergy can often mimic those of a common cold or other infections, clinical diagnosis is essential to identify the specific Allergen responsible. Management focuses on two main pillars: Avoidance and Medical Treatment.
Diagnostic Tests
- Skin Prick Test: Small amounts of suspected allergens are placed on the skin, which is then pricked. A small raised bump (wheal) indicates an allergy.
- Blood Test (IgE Test): Measures the amount of Immunoglobulin E antibodies in the blood produced in response to specific allergens.
- Elimination Diet: Used for food allergies, where suspected foods are removed and then gradually reintroduced one by one to monitor reactions.
Management Strategies
- Avoidance: The most effective way is to stay away from the trigger (e.g., using dust-proof covers, staying indoors during high pollen days).
- Anti-histamines: Drugs that block the action of histamines to reduce itching, sneezing, and swelling.
- Immunotherapy (Allergy Shots): Gradually exposing the body to increasing amounts of the allergen to desensitize the immune system over time.
Seasonal vs. Perennial: Seasonal allergies occur at specific times of the year (like Hay Fever during spring). Perennial allergies can occur year-round because the trigger is always present (like dust mites or pet dander).
Care and Precautions
| Allergen Type | Precautionary Measure | Key Treatment |
|---|---|---|
| Pollen | Keep windows closed; wear masks. | Nasal sprays. |
| Dust Mites | Regular vacuuming; wash bedding in hot water. | Antihistamine tablets. |
| Insect Venom | Avoid bright clothes/perfumes outdoors. | Adrenaline (EpiPen). |
Some scientists propose the Hygiene Hypothesis, suggesting that modern, extremely clean environments prevent children from being exposed to enough microbes. This "under-exposure" might cause the immune system to overreact to harmless substances later in life, leading to the rise in allergy cases.
In case of a severe reaction (Anaphylaxis), the person must be laid flat with their feet raised to maintain blood flow to the heart and brain while waiting for emergency medical help.
--- End of Advanced Study Notes: Allergy ---