- 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.