ICSE 7 Biology Allergy Basic

Allergy

Basic Study Notes

1.0 Introduction to Allergy

An allergy is an exaggerated or hypersensitive reaction of the immune system to certain substances found in the environment that are normally harmless to most people.

DEFINITION

Allergen: Any substance that causes an allergic reaction. Common examples include pollen, dust, and certain foods.

2.0 Common Allergens

Allergens can enter our body through different routes:

• Airborne Allergens: Pollen grains, dust mites, mold spores, and animal dander (skin flakes).
• Food Allergens: Peanuts, milk, eggs, seafood, and soy.
• Contact Allergens: Latex, certain cosmetics, and chemicals in soaps.
• Injected Allergens: Insect stings (bees/wasps) and certain medications like Penicillin.

3.0 How Allergy Occurs

When a sensitive person comes in contact with an allergen, their immune system produces a special type of antibody called IgE. These antibodies trigger certain cells to release a chemical called Histamine.

DEFINITION

Histamine: A chemical released by mast cells during an allergic reaction that causes symptoms like swelling, itching, and redness.

🔬 Did you know? Allergies are often hereditary. If both your parents have an allergy, there is a 75% chance that you might develop one too!

4.0 Symptoms of Allergy

Symptoms vary depending on the type of allergen and how it enters the body. They are generally categorized into three types:

1. Respiratory Symptoms

Caused by airborne allergens. Includes sneezing, running nose, watery eyes, coughing, and Asthma (difficulty in breathing).

2. Skin Symptoms

Caused by contact or food. Includes Urticaria (hives/red itchy bumps), rashes, and Eczema (dry, inflamed skin).

3. Digestive Symptoms

Caused by food allergens. Includes stomach pain, vomiting, diarrhea, and swelling of the lips or tongue.

5.0 Entry Routes of Allergens

Allergens can enter the body through four primary routes:

• 👃 Inhalation: Breathing in dust, pollen, or animal dander (affects nose and lungs).
• 👄 Ingestion: Eating or drinking allergic substances like nuts or milk (affects the digestive tract).
• ✋ Contact: Touching substances like latex, nickel, or cosmetics (affects the skin).
• 💉 Injection: Through insect stings or medicinal injections (spreads rapidly through the blood).

DEFINITION

Hay Fever: A common allergic condition caused by pollen or dust, characterized by sneezing and itchy, watery eyes.

🔬 Clinical Tip: Some allergies can cause a life-threatening reaction called Anaphylaxis, which requires immediate medical attention as it causes a sudden drop in blood pressure and difficulty breathing.

6.0 Diagnosis: Allergy Testing

To treat an allergy, we must first identify the specific allergen. Doctors use several methods:

• Skin Prick Test: A tiny amount of various allergens is placed on the skin (usually the forearm) and pricked with a needle. A small red bump indicates an allergy.
• Blood Test: Measures the amount of IgE antibodies in the blood to specific substances.
• Elimination Diet: Removing suspected foods from the diet one by one to see if symptoms disappear.

7.0 Prevention & Precautions

The best way to manage an allergy is avoidance.

DEFINITION

Antihistamines: Medicines that work by blocking the action of histamine to reduce allergic symptoms.

Daily Precautions:

• Keep the house free of dust and pet hair by regular vacuuming.
• Check food labels carefully for ingredients like nuts, soy, or dairy.
• Wear long sleeves and pants when walking in areas with high pollen or insects.
• Keep windows closed during high-pollen seasons (Spring/Autumn).

8.0 Emergency: Anaphylaxis

If a person experiences sudden swelling of the throat and difficulty breathing, follow these steps:

1. Call for emergency medical help immediately.
2. If they have an Epinephrine Auto-injector (EpiPen), help them use it.
3. Keep the person lying flat and warm until help arrives.

CHAPTER COMPLETED: ALLERGY

From Triggers and Symptoms to Diagnosis and Prevention.