Atopy

• Genetic predisposition to an exaggerated immune response to allergens.
• Overproduction of immunoglobulin E (IgE).
• Derived from Greek meaning “the state of being out of place”.

Atopic Triad

• Atopic dermatitis (skin)
• Asthma (airways)
• Allergic rhinitis (nasal mucosa)
• Other conditions: food and drug allergy, allergic conjunctivitis, urticaria, angioedema, anaphylaxis.

Who Gets Atopy?

• Prevalence: 10–30% in developed countries.
• Major risk factor: family history.
• Atopic diseases often coexist (atopic march).

Causes

• Gene-environment interaction.
• Triggers: viral respiratory infections, exercise, certain drugs, climatic and psychological factors.
• Involves mast cell activation leading to an inflammatory cascade.

Clinical Features

• Varies with specific atopic disease.
• Cutaneous features:
  • Atopic dermatitis: itchy, dry, scaly, thickened skin.
  • Other conditions: food and drug allergy, allergic conjunctivitis, urticaria, angioedema, anaphylaxis.

Clinical Features in Different Skin Types

• Higher prevalence in developed and industrialized countries.
• Hygiene hypothesis: lower incidence with early exposure to bacteria and protozoa.
• Immigrants at higher risk due to new allergen exposure.

Complications

• Varies with specific atopic disease.
• Atopic dermatitis
• Allergic rhinitis: sinusitis, otitis media.
• Asthma: pneumothorax, respiratory distress.
• Severe food allergy: anaphylaxis, medical emergency.

Diagnosis

• Usually clinical, investigations seldom required.
• Possible investigations:
  • Complete blood cell count (eosinophilia)
  • Prick testing or scratch testing
  • Specific IgE testing (ImmunoCAP, RAST)
  • Allergen provocation tests
  • Pulmonary function testing
• Differential diagnoses may require:
  • Quantitative serum immunoglobulins
  • Serum protein electrophoresis
  • Stool examination
  • Chest X-rays

Differential Diagnoses

• Chronic vasomotor rhinitis
• Pulmonary emphysema
• Allergic or irritant contact dermatitis and other eczema
• Lichen simplex chronicus
• Rare diseases: allergic bronchopulmonary aspergillosis, Job syndrome, IgE myeloma.

Treatment

• General Measures:
  • Patient education and counselling
  • Avoidance of allergens and irritants
  • Hydration
  • Good hygiene and proper skin care
• Specific Measures:
  • Atopic dermatitis: moisturizers, topical steroids, antibiotics for infections, phototherapy.
  • Severe cases: systemic immunosuppressants, biological agents, oral Janus kinase inhibitors.

Prevention

• Cannot be prevented due to genetic determination.
• Minimize symptoms with general measures and avoiding triggers.
• Insufficient data on probiotics for allergy prevention in children.

Outcome

• Generally good prognosis.
• Lifelong vulnerability of the immune system.
• Outcomes depend on severity and adherence to treatment.