Lecture: Allergy

Overview

Allergies, or allergic diseases, arise from hypersensitivity of the immune system to typically harmless environmental substances. Common allergies include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis.

Symptoms

• Red eyes
• Itchy rash
• Vomiting
• Runny nose
• Shortness of breath
• Swelling
• Sneezing
• Coughing

Causes

Common Allergens

• Pollen: Causes hay fever.
• Foods: Such as peanuts, tree nuts, milk, eggs, soy, wheat, fish, and shellfish.
• Dust Mites: Cause house dust allergy and can trigger asthma and eczema.
• Latex: Can cause contact dermatitis and severe systemic reactions.
• Medications: Common drugs include penicillin.
• Insect Stings: Can produce systemic allergic response (anaphylaxis).
• Environmental Factors: Pollution, dietary changes, and stress.

Genetic Factors

• Allergic diseases are familial with significant hereditary influences.
• Certain allergies are linked to irregularities in the immune system.

Pathophysiology

• Involves immunoglobulin E (IgE) antibodies.
• Mast cells and basophils release inflammatory chemicals like histamine.
• Acute response: Immediate effects like vasodilation, mucous secretion, and smooth muscle contraction.
• Late-phase response: Involves migration of leukocytes leading to prolonged inflammation.

Diagnosis

• Skin Prick Test: Checks for immediate allergic reactions.
• Patch Test: Used for diagnosing contact dermatitis.
• Blood Tests: Measures specific IgE antibodies.
• Challenge Testing: Controlled exposure to allergens.

Prevention

• Early exposure to potential allergens can be protective.
• Breastfeeding and diet regulation during infancy may reduce risk.

Management

• Avoidance: Key strategy to prevent allergic reactions.
• Medications: Include antihistamines, steroids, epinephrine, mast cell stabilizers, and antileukotrienes.
• Immunotherapy: Involves gradual exposure to allergens to desensitize the immune response.

Epidemiology

• Allergies are increasingly common.
• 20% affected by allergic rhinitis.
• Food allergies affect 10% of adults and 8% of children.

Historical Context

• The term "allergy" was first used by Clemens von Pirquet in 1906.

Research

• Ongoing research focuses on low-allergen foods and improving diagnostic tests.

Key Points

• The increasing prevalence of allergies in developed countries is partially attributed to the hygiene hypothesis.
• Stress and environmental changes also contribute to the rise in allergic diseases.

Takeaway

• Understanding the genetic, environmental, and immunological aspects of allergies is crucial for effective diagnosis, management, and prevention strategies.