Allergies Explained: Causes, Symptoms and Treatment Guide

An allergy is an exaggerated immune response to a harmless substance called an allergen, such as pollen, dust mites, peanuts or pet dander. The body mistakes it for danger and releases chemicals causing symptoms.

Allergies matter because asthma, hay fever, eczema and food allergy affect crores of people, and severe allergy called anaphylaxis can be life threatening within minutes but is treatable.

Key Concepts

Allergens are normally harmless proteins triggering IgE. IgE antibodies sit on mast cells. On re-exposure allergen cross-links IgE and mast cells release histamine, causing itching, sneezing, swelling and wheeze. Anaphylaxis is whole-body reaction with breathing difficulty and blood pressure fall. Types include respiratory, food, skin and drug allergies.

How It Works

1. First exposure sensitises: body makes IgE against allergen.
2. IgE attaches to mast cells in nose, lungs, skin and gut.
3. Next exposure allergen binds IgE and mast cells burst.
4. Histamine and other mediators cause symptoms in minutes.
5. Avoidance, antihistamines or adrenaline control reaction.

Worked Example

Consider peanut allergy dose. A sensitive child may react to as little as 1 milligram of peanut protein, about 1/250th of a peanut. Within 5 minutes lips swell, hives spread and wheezing begins. Adrenaline injection 0.15 mg for a 20 kg child using 1 mg per ml solution equals 0.15 ml intramuscularly, typically reverses airway swelling in 5-10 minutes. Antihistamine alone is too slow for anaphylaxis. The tiny dose versus severe response shows amplification by IgE and mast cells, and why carrying an adrenaline auto-injector saves lives.

Common Misconceptions

• Allergy and intolerance are same. Correction: lactose intolerance is enzyme deficiency, not IgE immune reaction.
• Allergies are always lifelong. Correction: milk and egg allergies in children often outgrow; peanut may persist.
• Antihistamines cure anaphylaxis. Correction: adrenaline is first treatment; antihistamines are secondary.

Real-World Applications

Diagnosis uses history, skin prick and IgE blood tests. Management is allergen avoidance, antihistamines, inhalers for asthma, immunotherapy desensitisation and emergency adrenaline. Food labelling laws require declaring major allergens. Schools keep allergy action plans for at-risk children.

Indoor allergen control includes encasing mattresses, washing bedding weekly in hot water and reducing dust-collecting clutter in bedrooms. Asthma action plans specify daily controller inhalers and rescue inhaler steps during attacks triggered by allergens. Reading ingredient labels carefully and informing restaurants about food allergy prevents accidental exposure, since even trace cross-contact during cooking can trigger reactions in highly sensitive individuals within minutes.

Allergy is IgE-driven overreaction to harmless substances; recognising triggers, using correct medicines and emergency adrenaline keeps it controlled.