Allergy (General principles)

Question 1

What confers susceptibility to allergy

Answer 1

Polymorphisms in various genes confer susceptibility. Additionally, the developing immune system must be sensitised to an allergen before an allergic immune response develops- may be in response to trace quantities

Question 2

Clinical course of IgE mediated reactions

Answer 2

• Early phase- occurs within minutes of exposure to the allergen and stimulates the release of histamine and other mast cell inflammatory mediators, leads to: urticaria, angioedema, sneezing, vomiting, bronchospasm and CV shock
• Late phase- may occur after 4-6 hours- especially after reaction to inhaled allergens. Get nasal congestion in the upper airway, cough and bronchospasm in the lower airway

Most severe life-treatening allergic reactions are IgE mediated

Question 3

Definition of hypersensitivity

Answer 3

Objectively reproducible signs and symptoms following exposure to a defined stimulus at a dose which is usually tolerated by most people

Question 4

Definition of allergy

Answer 4

A hypesensitivity reaction initiated by specific immunological mechanisms- IgE mediated or non-IgE mediated (e.g coeliac)

Question 5

Definition of atopy

Answer 5

A personal and/or familial tendancy to produce IgE antibodies in response to ordinary exposure to potential allergens, usually proteins- strongly associated with asthma, allergic rhinitis and conjunctivitis, eczema and food allergy

Question 6

Definition of anaphylaxis

Answer 6

A serious allergic reaction with bronchial, laryngeal or cardiovascular involvement that is rapid in onset and may cause death

Question 7

What is the clincial course of atopic march

Answer 7

Children with atopy will develop individual allergic disorders at different ages:
* INFANCY- Eczema, Food allergy
* PRIMARY SCHOOL YEARS- Allergic rhinitis, Conjunctivitis, Asthma
* Rhinitis and conjunctivitis may proceed the development of asthma, however most of these conditions will overlap

Question 8

What are the signs of atopy

Answer 8

• Mouth breathing- breathing habitually through the mouth may be an indication of obstruction of the airway due to rhinitis
• Allergic salute- rubbing the nose upwards
• Atopic eczema affecting the limb flexures
• Hyperinflated chest or Harrison’s sulcus (indentation along the lower border of the thorax) are indications of chronic untreated asthma
• Malnutrition/ poor growth- where dietary restriction or malabsorption can lead to nutritional compromise
• Food allergy should be considered in children who do NOT respond to treatment for atopic eczema, GORD, chronic GI symptoms