Flashcards in Allergy Deck (16)
What must happen in a developing immune system for an allergic immune response to develop?
The developing immune system must be sensitised to an allergen - can be occult eg. Exposure to trace amounts of egg in maternal breast milk
What is usually the stimuli for allergic response?
Abnormal immune response usually to a protein
What is atopy?
A personal or familial tendency to produce IgE antibodies in response to ordinary exposures to potential allergens - usually proteins
What are the two characteristic phases of an IgE-mediated allergic reaction
Early phase occurring within minutes of exposure to allergen- caused by release of histamine and mast cells - urticaria, angioedema, sneezing and bronchospasm
Late phase after 4-6 hours - nasal congestion of upper airway, cough and bronchospasm in lower airway
What is a non IgE mediated response like?
Delayed response and varied clinical course, not life threatening
What is the allergic March?
Allergic children develop different individual allergic disorders at different ages
What part of the allergic March happens in infancy?
Eczema and food allergy develop in infancy and both usually occur
What part of allergic March occurs in preschool and primary school years?
Allergic rhinitis and conjunctivitis and then followed by development of asthma
Signs of an allergic child
Mouth breathing due to congested nose
Allergic salute with crease on nasal bridge
Always being nasally congested (parents may not think this is abnormal)
Eczema in limb flexures
Hyper inflated chest from undertreated asthma
Pale and swollen inferior nasal turbinates
What is best method for immunotherapy
Sublingual administration of solutions of allergen regularly for 3-5 years - so far not for food allergens
Two types of food allergy
Primary where child has failed to ever develop immune tolerance to the food
Secondary where children initially tolerate the food and then later become allergic. Usually due to cross reactivity between similar proteins in different allergens such as fruit and pollen 'pollen fruit syndrome'
How does non-IgE mediated food allergy usually present?
Diarrhoea, vomiting, abdominal pain and sometimes failure to thrive
May also have colic and eczema
Also sometimes blood in stools in first few weeks of life from proctitis
What is cough variant rhinitis
A form of rhino conjunctivitis where there is also cough due to post nasal drip
Are acute and chronic urticaria allergic in origin in normally?
Acute yes but chronic aka >6 weeks not usually - instead chronic arises from local increase in permeability of capillaries and venules
What sort of reactions can there be with insect sting hypersensitivity?
Mild eg. Local swelling
Moderate eg. Generalised urticaria
Severe eg. Systemic requiring adrenaline
A mild or moderate usually doesn't progress to severe in future