Allergy is a type 1 hypersensitivity reaction to certain environmental allergens.
Why is the incidence of allergy rising in developed countries?
- Hygiene Theory. People arn’t building up a tolerance to environmental antigens as children due to better hygiene.
- Our diet becoming more processed
What are the risk factors for allergy?
- Certain Dietary Changes
- Allergen Levels
- Altered exposure to infectious diseases in early childhood
- Environmental pollution
- E.g. exposure to flour, latex or wood dust
How do allergic reactions vary?
They can be local or systemic.
They vary based on:
- Mode of introduction
Define an allergen?
The particle who’s antigen triggers the allergic reaction.
Usually they’re proteins
Explain how an allergy develops and a reaction occurs?
1) On 1st exposure plasma cells produce specific IgE antibodies (i.e. becoming sensitized)
2) IgE binds to mast cells
3) On re-exposure they trigger the mast cells to degranulate, giving out histamine, leukotrienes, prostaglandins & Chemotactic factors
4) Inflammatory response occurs
Explain the phases of an allergic reaction?
- Acute Inflammation
- If systemic can be anaphylaxis
- 2-4 hours later
- Occurs due to migration of distant leukocytes (e.g. neutrophils, lymphocytes, eosinophils & macrophages)
How do we classify allergy>
Using the ARIA classification
Split into intermittent vs persistent
And Mild vs Moderate/severe
What makes an allergy intermittent or persistent?
- OR <4 consecutive wks
- 4 or more days/wk
- AND 4 or more consecutive wks
How do we divide allergies into mild or moderate-severe?
Its moderate-severe if:
- Sleep Disturbances
- Impairs Daily Activities
- Impairs Work or school
- Symptoms are troublesome
How do we diagnose an allergy?
Allergic Skin Test:
- Tests skin response to known allergens
Radioallergosorbent Blood Test:
- Tests for presence & level of allergen specific IgE
- Total Serum IgE
- Nasal Allergen Challenge
- Nasal Cytology
How do we treat Allergies?
Allergen Avoidance is First line.
Salty Water (Saline) Spray
- Steroids (topical vs systemic)
- Sodium Cromoglycate
Define Allergic Rhinitis?
Allergic Inflammation of the Nasal Airways
Occurs when a person with a sensitized immune system breaths the allergen in
What are the risk factors for Allergic Rhinitis?
- Environmental (Same as general allergy risk factors)
- Atopy (i.e. associated with other atopic disease e.g. eczema/asthma)
- 1st Born
- Family History
What are the symptoms of allergic rhinitis?
- Nasal Blockage
- Chronic Obstruction
- Hyposmia (Reduced smell due to nasal blockage preventing air flow to olfactory nerves)