Allergies

What is an allergy?

An allergy is the body's reaction to a substance (allergen) that is usually harmless — mistaking it for a threat. When you come in contact with the allergen, your immune system releases chemicals like histamine, which cause symptoms. Common allergies are to dust mites, pollen, pet dander, mould, certain foods, insect stings, and medicines.

Common allergens in India

• Dust mites and cockroach allergens — very common in humid Indian cities; major trigger for asthma and rhinitis
• Pollen — seasonal (tree pollen in spring, grasses and weeds later). Mustard pollen is a notable Indian allergen.
• Fungal (mould) spores — rise during monsoon
• Pet dander — cat, dog, and sometimes buffalo/cow hair in rural settings
• Foods — cow's milk, egg, peanuts, tree nuts, soya, wheat, fish, shellfish are the common global offenders; in India, milk and wheat are especially common in children
• Medicines — penicillin, NSAIDs, certain contrast dyes
• Insect stings — honeybee, wasp

What are the symptoms?

Symptoms depend on the allergen and the part of the body affected:

• Respiratory — sneezing, runny or blocked nose, itchy eyes, cough, wheeze (allergic rhinitis, asthma)
• Skin — hives (urticaria), eczema, itching, swelling
• Digestive — vomiting, diarrhoea, stomach pain (food allergies)
• Severe — anaphylaxis: sudden swelling of the face/tongue/throat, difficulty breathing, rapid pulse, loss of consciousness. Life-threatening and needs immediate hospital care. Dial 112.

How are allergies diagnosed?

A doctor will ask about your symptoms and possible triggers. Tests may include:

• Skin prick test — small amounts of suspected allergens applied to the skin
• Blood test (specific IgE) — looks at your immune response to specific allergens
• Elimination diet, for suspected food allergies

Treatment and prevention

• Avoidance — the single most effective step. Reduce dust mites by using mattress covers, washing bedding in hot water weekly, minimising carpeting, using HEPA filters if possible.
• Medicines — antihistamines and nasal steroid sprays, inhalers for asthma. Follow your doctor's plan.
• Immunotherapy (allergy shots or sublingual tablets) — for severe allergies not controlled by medicines. Available in major Indian allergy centres.
• For known severe food allergy or insect sting allergy: carry an epinephrine auto-injector (adrenaline pen) if prescribed, and a medical ID. Educate family and school about what to do in an emergency.