Immunology Flashcards
What is anaphylaxis?
Anaphylaxis is a life-threatening medical emergency caused by a severe type 1 hypersensitivity reaction.
What triggers anaphylaxis at the immunological level?
Anaphylaxis is triggered when Immunoglobulin E (IgE) stimulates mast cells to rapidly release histamine and other pro-inflammatory chemicals, a process known as mast cell degranulation
Describe the presentation of anaphylaxis
sudden onset and rapid progression of symptoms
* airway: swelling of the throat and tongue →hoarse voice and stridor
* breathing: dyspnoea and wheeze
* circulation: hypotension, tachycardia
additional symptoms:
* widespread erythematous or urticarial rash
* generalised Itching
* Angioedema (swelling around lips and eyes)
What is the initial step in managing anaphylaxis?
IM adrenaline (repeated after 5 minutes if required)
How can anaphylaxis be confirmed?
- measuring serum mast cell tryptase within 12 hours of the event
- Tryptase is released during mast cell degranulation and levels rise following an acute episode
How should an adrenaline auto-injector be used in anaphylaxis?
- Firmly jab the device into the anterolateral aspect of the middle of the thigh until it clicks (can be done through clothing)
- A second dose may be given (with a new pen) after 5 minutes if required
How is anaphylaxis managed following stabilisation
- non-sedating oral antihistamines
- all patients with a new diagnosis of anaphylaxis should be referred to a specialist allergy clinic
- adrenaline injector: patients should be prescribed 2 adrenaline auto-injectors, training should be provided on how to use it
- a risk-stratified approach to discharge
Why should a risk-stratified approach to discharge be taken in anaphylaxis patients
biphasic reactions can occur in up to 20% of patients
What is refractory anaphylaxis
defined as respiratory and/or cardiovascular problems that persist despite 2 doses of IM adrenaline
How is refractory anaphylaxis managed
- IV fluids should be given for shock
- expert help should be sought for consideration of an IV adrenaline infusion
What is allergic rhinitis?
a condition caused by an IgE-mediated type 1 hypersensitivity reaction, resulting in an allergic inflammatory response in the nasal mucosa
What are the types of allergic rhinitis?
- Seasonal: For example, hay fever.
- Perennial: Year-round, such as house dust mite allergy.
- Occupational: Associated with allergens in the school or work environment.
What are the typical symptoms of allergic rhinitis?
- Runny, blocked, and itchy nose
- Sneezing
- Itchy, red, and swollen eyes
What personal history is often associated with allergic rhinitis?
commonly associated with a personal or family history of other allergic conditions (atopy).
What is the first step in managing allergic rhinitis?
Avoid the trigger. Actions include:
* Hoovering and changing pillows regularly.
* Ensuring good ventilation of the home.
* Staying indoors during high pollen counts.
* Minimizing contact with known allergy-triggering pets.
What oral antihistamines are used for allergic rhinitis?
- Non-sedating antihistamines: Cetirizine, loratadine, fexofenadine.
- Sedating antihistamines: Chlorphenamine (Piriton), promethazine.
What nasal medications can help manage allergic rhinitis?
- Nasal corticosteroid sprays (e.g., fluticasone, mometasone) to suppress local allergic symptoms.
- Nasal antihistamines for rapid onset symptoms in response to triggers.
What is cow’s milk protein allergy?
a condition typically affecting infants and young children under 3 years, involving hypersensitivity to the protein in cow’s milk
What are the two types of reactions associated with cow’s milk protein allergy?
- IgE-mediated: Rapid reactions occur within 2 hours of ingestion (allergy)
- Non-IgE mediated: Reactions occur slowly over several days (intolerance)
What type of feeding increases the risk of cow’s milk protein allergy in infants?
more common in formula-fed babies
What are the features of cow’s milk protein allergy?
- GI: regurgitation, vomiting, diarrhoea
- Skin: urticaria, atopic eczema
- Behavioural: irritability, “colic” symptoms
- Respiratory: wheezing, chronic cough
- Rare reactions: angioedema, anaphylaxis
How is cow’s milk allergy managed
- extensive hydrolysed formula (eHF) milk for infants with mild-moderate symptoms
- amino acid-based formula (AAF) in infants with severe CMPA
- continue breastfeeding but eliminate cow’s milk protein from maternal diet
- Consider prescribing calcium supplements for breastfeeding mothers
- Every 6 months or so, infants can be tried on the first step of the milk ladder
What is the typical prognosis for children with cow’s milk protein allergy
- usually resolves in most children.
- IgE-mediated: Most will be milk tolerant by age 5.
- Non-IgE mediated: Most will be milk tolerant by age 3.
Give 3 contraindications to immunisation
- confirmed anaphylactic reaction to a previous dose of a vaccine containing the same antigens
- confirmed anaphylactic reaction to another component contained in the relevant vaccine (e.g. egg protein)
- Live vaccines: pregnancy and immunosuppression
What vaccines are given to babies under 1 year old in the UK?
- 8 weeks: 6-in-1 vaccine, Rotavirus vaccine, MenB vaccine
- 12 weeks: 6-in-1 (2nd dose), Pneumococcal vaccine, Rotavirus (2nd dose)
- 16 weeks: 6-in-1 (3rd dose), MenB (2nd dose)
What 6 illnesses does the 6-in-1 vaccine protect babies against?
- Diphtheria
- Hepatitis B
- Hib (Haemophilus influenzae type b)
- Polio
- Tetanus
- Whooping cough
What vaccines are given to children aged 1 in the UK
- Hib/MenC (1st dose)
- MMR (1st dose)
- Pneumococcal (2nd dose)
- Meningococcal B (3rd dose)
What vaccines are given at 3 years and 4 months, and at 12-13 and 14 years in the UK?
- 3 years and 4 months: MMR (2nd dose), 4-in-1 preschool booster (diphtheria, tetanus, whooping cough and polio)
- 12-13 years: HPV vaccine
- 14 years: Tetanus, diphtheria and polio (3-in-1 teenage booster), MenACWY vaccine
