Immunology: Allergy / Allergic Reactions Flashcards
What does atopy mean? [1]
How does it differ from allergy [1]
Atopy - IgE mediated exaggerated immune response
Allergy - mediated exaggerated immune response
What are NICE indications for an allergy referal if a patient has eczema? [3]
Moderate or severe atopic eczema and suspected food allergy
Suspect food allergy if:
- reacted previously to a food with immediate symptoms
- infants / young children with moderate / severe atopic eczema that has not been controlled by optimum management, particularly if associated with gut dysmotility (colic, vomiting, altered bowel habit) or failure to thrive.
Suspect inhalant allergy if:
- seasonal flares of atopic eczema
- children with atopic eczema associated with asthma or allergic rhinitis
- children aged 3 years or over with atopic eczema on the face, particularly around the eyes.
What increases the chance of allergy in eczema? [6]
- Atopic FHx
- Early onset of eczema
- Severity of eczema
- Resistant to tx
- GI symptoms (increases chances of non-IgE allergy)
- Faltering growth
What is important to note about itch and eczema [1]
Just because they itch, doesn’t mean they have an allergic reaction
- Itch in eczema is caused by non-histamines until it is itched (and then histamines are released)
Which food allergy is most common in a child [1] and adulthood [1]
Children: cow’s milk
Adulthood: Peanuts
Describe the EATERS Hx taking tool [6]
Exposure:
- eaten / handled food?
- kissed or touched by smeone with food?
- aerosolised allergens?
Allergen:
- Ask about common allergens - milk, egg, nuts, soya, wheat
- Prawns and shelffish more common in older
Timing:
- Most IgE mediated reactions occur within 15 mins
- Can be delayed by an hr if covered in fatty substance
Environment:
- Weaning from milk –> solids is common time for presention
- Most reactions occurs at restaurants / takeaways
Reproducible symptoms:
- Most reactions occur at all exposures to food
- In infancy, may tolerate initially but reaction on next exposure. If have since tolerated, is unlikely to be that food allergy
Symptoms:
- Skin: hives, redness, swelling, itch,
- Gut: vominting, abdo pain, diarrhoea
- Resp: rhinorrhoea, cough, wheeze, stridor
- NeurologicalL change in behaviour, sleepiness, doom feeling
- CV: shock and collapse
Risk Factors:
- Eczema, asthma, food allergy and allergic rhinitis
What are NICE indications for referral for food allergy? [7]
- faltering growth in combination with one or more of gastrointestinal symptoms
- had one or more acute systemic reactions
- had one or more severe delayed reactions
- confirmed IgE-mediated food allergy and concurrent asthma
- significant atopic eczema where multiple / cross-reactive food allergies are suspected
- strong clinical suspicion of IgE-mediated food allergy but allergy test results are negative
- clinical suspicion of multiple food allergies.
Which components of an asthmatics Hx / diseaese profile would indicate that there is an allergic airways component? [6]
Allergic trigger
Atopic hx
+VE IgE
High FeNO
Allergic rhinitis
Steroid helps tx symptoms
What are the 4 different overlying causes of rhinitis [4]
What would help differentiate towards them? [4]
What are key clinical features of allergic rhinitis? [2]
Swollen, red mucuosa & septum
Enlarged inferior turbinate (in chronic inflammation this will be white)
How do nasal polyps present differently to allergic rhinitis when looking up nose? [1]
What are the different forms of classifying allergic rhinitis? [3]
Mild
- Normal sleep, daily activities, work and school, no troublesome symptoms
Moderate - Severe: (one or more of)
- Abnormal sleep
- Impairment of daily activities, sport or leisure
- Problems caused at school
- Troublesome symptoms
They can either be intermittent (< 4 days a week or < 4 weeks at a time) or persistent (>days/week and > 4 weeks at a time)
Describe what is meant by spectrum of allergic reaction and anaphylaxis [1]
Allergic reactions have a spectrum of severity which is mild to severe (anaphylactic).
- But anaphylactic end also has a spectrum, at the severe end if anaphylactic shock
In an A-E, what would determine a patient is suffering from anaphylaxis? [3]
A:
- persistent cough
- horse voice
- difficulty swallowing
- swollen tongue
B:
- Difficulty or noisy breathing
- Wheezing
C:
- Feeling lightheaded or faint
- Clammy skin
- Confusion
- BP drop
Describe what is meant by the bi-phasic anaphylaxis reaction [2]
What increases the chance of it occurring? [[3]
After initial symptoms (and treatment), about 12 hours after the initial reaction, 2nd less severe reaction occurs
Increased chance if:
- needed multiple doses of adrenaline
- delay in adrenaline administration
- previous bi-phasic reaction
NB: quite rare,
When do you give adrenaline to patients [3]
Hx of anaphylaxis
Minor reaction but has significant risk factor like asthma
Reacted to traces of a food
Explain the three main ways to test for allergy? [3]
Skin prick testing
- A drop of each allergen solution is placed at marked points along the patch of skin, along with a water control and a histamine control. A fresh needle is used to make a tiny break in the skin at the site of each allergen. After 15 minutes, the size of the wheals to each allergen are assessed and compared to the controls.
RAST testing
- RAST testing measures the total and allergen specific IgE quantities in the patient’s blood sample.
Food challenge testing
- The child is gradually given increasing quantities of an allergen to assess the reaction starting with almost non-existent quantities diluted further in other foods, for example mixing a small amount of peanut into a bar of chocolate. Children are monitored very closely after each exposure. This can be very helpful in excluding allergies for reassurance.
What are skin prick and RAST testing specifically assessing? [1]
Skin prick testing and RAST testing assess sensitisation and NOT allergy. This is important, because it makes these tests notoriously unreliable and misleading.
What is the gold standard investigation for dx allergy? [1]
Foot challenge testing is the gold standard investigation for diagnosing allergy, however it requires a lot of time and resources and is only available in selected places.
What is important to note about skin prick test? [1]
Can’t have taken anti-histamines prior to test
How do you treat:
- Mild allergic reactions [2]
- Severe allergic reactions [2]
Mild allergic reactions:
- Antihistamines
- Corticosteroids
Severe allergic reactions:
- IM adrenaline 0.5-1mg
- IV hydrocortisone
Describe when and how many samples of mast cell tryptase you should take [+]
Mast cell tryptase is one of the major proteins released during activation and degranulation
Immediate sample: taken as soon as possible after onset. Should NOT delay treatment
Second sample: taken at 1-2 hours after onset. Should be no later than 4 hours. Minimum required sample
Third sample:taken at least 24 hours after onset. Often taken at follow-up allergy clinic. Acts as the baseline level
Describe the treatment protocol in emergency anaphylaxis [4]
NB in adults
ABCDE
1. IM adrenaline 1mg/ml (1:1000) in anterolateral aspect middle of thigh
2. Establish airway & give high flow O2
3. If no response - repeat IM adrenaline after 5 minutes & IV fluid bolus
4. If no improvement after 2 doses of adrenaline - follow refractory algorithm
What are the doses for IM adrenaline for:
Adults and children > 12
6-12 year olds
6 months - 6 years
< 6 months
Adult and child >12 years old:
- 500 micrograms IM (0.5 mL of 1mg/mL adrenaline)
6-12 years old:
- 300 micrograms IM (0.3 mL of 1mg/mL adrenaline)
6 months - 6 years:
- 150 micrograms IM (0.15 mL of 1mg/mL adrenaline)
< 6 months:
- 100-150 micrograms IM (0.1-0.15 mL of 1mg/mL adrenaline)
How does adrenaline work to treat anaphylaxis? [2]
Alpha-adrenergic receptors:
- causes vasoconstriction that reverses peripheral vasodilation and reduces tissue oedema
Beta-adrenergic receptors:
- causes bronchodilation, increases myocardial contractility and suppresses histamine/leukotriene release. Also inhibits mast cell activation
How do you treat refractory anaphylaxis? [1]
The principal treatment is initiation of an adrenaline infusion.
Repeated doses of intramuscular adrenaline should be given at 5 minute intervals whilst the intravenous infusion is being prepared and ongoing fluid resuscitation should be administered.
Serum tryptase
A 5-year-old boy is brought to the emergency department with sudden onset wheezing and swelling of his tongue, face and hands. On assessment there is evidence of airway compromise.
What is the correct dose of 1 in 1,000 intramuscular adrenaline to treat this patient?
150 micrograms
150 milligrams
500 micrograms
500 milligrams
1000 micrograms
150 micrograms
You are called to the treatment room of a GP surgery as a 12-month-old boy has developed a rash and breathing difficulties following a routine vaccination. On examination he is developing swelling around the mouth and neck. What is the most appropriate initial action?
Phone 999 and reassure mother
IM adrenaline 150 mcg (0.15ml of 1 in 1,000)
IM adrenaline 300 mcg (0.3ml of 1 in 1,000)
IM adrenaline 50 mcg (0.05ml of 1 in 1,000)
Salbutamol nebuliser stat
IM adrenaline 150 mcg (0.15ml of 1 in 1,000)
6 months - 6 years adrenaline dose for anaphylaxis 150 mcg (0.15ml 1 in 1,000)
In the treatment of anaphylaxis, you can repeat adrenaline every [] minutes
5 minutes
TOM TIP: Remember to measure mast cell tryptase within [] hours of an anaphylactic reaction. This is a common exam question and also something that will impress senior colleagues if it is part of your management plan when managing children with anaphylaxis.
TOM TIP: Remember to measure mast cell tryptase within 6 hours of an anaphylactic reaction. This is a common exam question and also something that will impress senior colleagues if it is part of your management plan when managing children with anaphylaxis.
Describe how you use an Adrenalin Auto-Injector [6]
How to Use an Adrenalin Auto-Injector:
* The first step is to confirm the diagnosis of anaphylaxis.
* Prepare the device by removing the safety cap on the non-needle end. There is a blue cap on EpiPen and a yellow cap on Jext.
* Grip the device in a fist with the needle end pointing downwards. The needle end is orange on EpiPen and black on Jext. Do not put your thumb over the end, because if the device is upside down you will inject your thumb with adrenalin and could risk losing it.
* Administer the injection by firmly jabbing the device into the outer portion of the mid thigh until the device clicks. This can be done through clothing. EpiPen advise holding it in place for 3 seconds and Jext advise 10 seconds before removing the device.
* Remove the device and gently massage the area for 10 seconds.
* Phone an emergency ambulance. A second dose may be given (with a new pen) after 5 minutes if required.
Define refractory anaphylaxis [1]
Refractory anaphylaxis
* defined as respiratory and/or cardiovascular problems persist despite 2 doses of IM adrenaline
Describe the treatment algorithm for refractory anaphylaxis [+]
The Resus Council UK recommend the following risk-stratified approach to discharge:
fast-track discharge (after 2 hours of symptom resolution): [3]
adequate supervision following discharge [2]
minimum 12 hours after symptom resolution [6]
fast-track discharge (after 2 hours of symptom resolution):
* good response to a single dose of adrenaline
* complete resolution of symptoms
* has been given an adrenaline auto-injector and trained how to use it
adequate supervision following discharge
minimum 6 hours after symptom resolution:
* 2 doses of IM adrenaline needed, or
* previous biphasic reaction
minimum 12 hours after symptom resolution:
* severe reaction requiring > 2 doses of IM adrenaline
* patient has severe asthma
* possibility of an ongoing reaction (e.g. slow-release medication)
* patient presents late at night
* patient in areas where access to emergency access care may be difficult
* observation for at 12 hours following symptom resolution
