Allergy Flashcards
Define Hypersensitivity
Objectively reproducible signs and symptoms following exposure to a stimulus that is tolerated by most
Define Allergy
Hypersensitivity reaction initiated by specific immunological mechanisms
Can be IgE or non IgE mediated
Define Atopy
Personal and or familial tendency to produce IgE AB in response to ordinary exposures to potential allergens
Define Anaphylaxis
Serious allergic reaction with bronchial/laryngeal/CVS involvement that is rapid in onset and may cause death
Describe the mechanism of an IgE Mediated Allergic reaction
Early phase occurring within minutes of exposure caused by histamine release (eg angio-oedema, urticaria)
Late phase after 4-6 hours (Nasal Congestion)
Describe the mechanism of an Non IgE Mediated Allergic reaction
Delayed onset of symptoms and more varied course
What is the Hygiene Hypothesis?
Family Size/Parasite exposure/Infections/Antibiotics/Farming exposure all determines microbiological exposure and allergy risk
Describe the ‘Allergic March’
Eczema and food allergy develop in infancy
Allergic Rhinitis/Asthma begin in preschool
Describe some novel preventative theories regarding allergies
Probiotics during late pregnancy and lactation to prevent eczema
Early introduction of peanut/egg
State four things that might be seen in an allergy examination (non acute)
Mouth Breathing (due to nasal congestion)
Allergic Salute (rubbing an itchy nose)
Pale and Swollen inferior turbinates
Atopic Eczema
How can Immunotolerance be increased?
Solutions of allergen to which patients are allergic are given subcut/sublingually on a regular basis for 3-5 years
Define Food Allergy
Pathological immune response mounted against specific food protein
Usually IgE mediated but can be non IgE
Define Food Intolerance
Non immunological hypersensitivity to a specific food
Allergies can be Primary or Secondary, what is the difference?
Primary - Children react on first exposure (younger - milk and eggs, older - peanuts and fish)
Secondary - Cross reactivity between proteins present in fresh fruit/veg/nuts and those present in pollens (AKA Pollen Food Syndrome)
How does an IgE Food Allergy present?
- Varies from Urticaria, to facial swelling to Angio-oedema
- Normally within 10-15 minutes of ingestion
Food Associated Exercise Induced allergy is a specific type of IgE allergy, how does it present?
Food triggers anaphylaxis but only if ingestion is followed by exercise within two hours
How does Non IgE food allergy present?
Occurs later after ingestion and tends to resolve earlier
Diarrhoea, Vomiting, Abdominal Pain, Faltering Growth
Food Protein Induced Enterocolitis Syndrome is a specific type of Non IgE Food Allergy, how does it present?
Profuse vomiting potentially leading to shock
How are IgE and non IgE food allergies diagnosed respectively?
IgE - skin prick tests, specific IgE levels in blood
Non IgE - harder to diagnose so generally reliant on clinical history and exam, can do intestinal biopsy
Why can you have a positive wheal on skin prick test without symptoms?
Sensitisation
How are Food Allergies managed?
Avoidance of known triggers (inc cross allergies)
Management plan for parents and child (mild - antihistamines, severe - epipen)
What is the prognosis of food allergies?
Food allergy to Cows Milk and Egg normally resolves in childhood
Nuts and Seafood allergy persists
What is Cows Milk Protein Allergy?
Immune mediated allergic response to naturally occurring milk proteins (Casein and Whey)
CMPA can be IgE or Non IgE, and present in the classical ways. What is the different reaction pathways?
IgE Mediated - Type One Hypersensitivity caused by B cells producing IgE which trigger histamine and cytokine release
Non IgE Mediated - T Cell Activation
Describe five features of an allergy focussed history
Atopy FH Infants diet and feeding Mothers diet if breast fed Age of onset Which Milk/Formula
Give three examinations that should be done on suspected CMPA
General GI Exam
Growth Charts
Atopic Comorbidities
How is CMPA diagnosed?
Normally a clinical diagnosis
Referred for IgE if faltering growth, >1 reaction, persistent parental suspicion
How is CMPA managed?
Avoidance of Cows Milk in all forms (including mothers diet if breast fed)
Reassess every 6-12m
How is CMPA managed if they are formula fed?
Extensively Hydrolysed Formula (cheaper’
Amino Acid Formula (second line, more expensive)
Why is Soya Based Formula not recommended in CMPA?
Weak oestrogenic effect
Phytate may inhibit mineral and element absorption
Describe the Milk Ladder for non IgE CMPA
1) Cookie
2) Muffin
3) Pancake
4) Cheese
5) Yoghurt
6) Pasteurised Milk
What is Lactose Intolerance?
Result of enzyme deficiency rather than IgE mediated
Rarely presents in <6 y
What are the four types of Lactose Intolerance?
Primary - Autosomal recessive and develops at various ages
Secondary - following damage to intestinal mucosa
Congenital - Rare, Autosomal Recessive
Developmental - in premature babies, improves as intestine matures
How does Lactose Intolerance present?
Bloating, Flatulence, Abdominal Discomfort, Loose Watery Stools
Failure to thrive
How is Lactose Intolerance normally diagnosed?
Generally clinical - trial of two weeks lactose free followed by symptoms on reintroduction
What is the ‘Lactose Tolerance Test’?
Dose of 2g/kg of lactose (up to 50g)
Note the blood sugar, if positive, the BGC shouldn’t rise and there should be an onset of symptoms
What is one investigation other than the Lactose Tolerance Test that could be used to diagnose Lactose Intolerance
Hydrogen breath test
Hydrogen is a by product of bacterial fermentation of undigested lactose
How is Primary Lactose Intolerance managed?
Avoidance of lactose to varying extents
Higher fat content is better tolerated as it slows gastric emptying
How is Secondary Lactose Intolerance managed?
Fluid rescucitation may be required
How is Developmental Lactose Intolerance managed?
Full lactose feeds are more likely to induce tolerance
How is Congenital Lactose Intolerance managed?
Cannot breast feed
Requires lactose free formula and subsequently food
What electrolytes may be low as a complication from Lactose Intolerance?
Calcium
Magnesium
Zinc
Define Anaphylaxis
Severe life threatening systemic type 1 hypersensitivity reaction
Anaphylaxis will initially be managed with an A to E assessment. What interventions are likely?
- Secure airway
- Consider Oxygen
- IV fluid bolus
- Lie patient flat to promote cerebral perfusion
State the medication required in an Anaphylactic reaction (adult doses)
0.5ml 1:1000 Adrenaline IM
100-300mg IV Hydrocortisone
10mg IV/IM Chlorphenamine
After the initial management, how should the child suffering anaphylaxis be treated?
Admit to Paediatric Ward (biphasic reaction)
Confirm by measuring serum tryptase within 6 hours
Define Allergic Rhinitis
IgE mediated type 1 hypersensitivity causing an inflammatory response in the nasal mucosa
Can be seasonal, perennial or occupational
How is Allergic Rhinitis managed?
Avoid the trigger (hoover and change pillows regularly, staying indoors in high pollen count)
Oral Antihistamines
Nasal Sprays (don’t sniff) (fluticasone or antihistamine)
Give examples of the different types of antihistamine
Non Sedating - Cetirizine, Loratidine
Sedating - Chlorphenamine, Promethazine
Define Urticaria
Itchy red blotchy rash from swelling of superficial skin (secondary to mast cell activation)
(Called Angio-oedema when it affects deeper tissues)
Describe the appearance of Urticaria
Itchy white papule/plaque surrounded by erythematous flare
How is Urticaria managed?
Avoid aggravating factors (overheating, stress) Topical Antipruritics (Calamine or topical menthol) Non sedating antihistamines (3-6 months)
If severe can give oral steroids
