Allergies Flashcards
What is an allergic disorder?
An exaggerated immune response to normally harmless substances (allergens) mediated by IgE antibodies. An allergy refers to an inappropriate, exaggerated immune response against ordinarily harmless substances present in the environment.
What is an allergen?
A normally harmless substance that triggers an allergic response in susceptible individuals.
What are common allergens that trigger allergic reactions?
Airborne allergens (pollen, dust mites, pet dander).
Food allergens (peanuts, shellfish, dairy, eggs).
Insect venom (bee, wasp stings).
Medications (penicillin, NSAIDs).
Latex.
What are risk factors for developing allergic disorders?
Genetic predisposition (family history of allergies).
Atopy (personal history of eczema, asthma, allergic rhinitis).
Environmental exposure (pollution, smoking).
Early-life factors (C-section birth, lack of breastfeeding).
What are the key steps in the allergic response?
Sensitization phase: First exposure leads to IgE antibody production.
Re-exposure: Allergen binds to IgE on mast cells.
Mast cell degranulation: Release of histamine and inflammatory mediators.
Clinical symptoms: Swelling, itching, bronchoconstriction, anaphylaxis.
The key immune cells involved in allergic reactions are __________ and __________.
mast cells, eosinophils
What role does histamine play in allergic reactions?
It increases vascular permeability, leading to swelling, redness, and itching.
What are the different types of allergic disorders?
Allergic rhinitis (hay fever).
Asthma (allergic component).
Atopic dermatitis (eczema).
Food allergies.
Anaphylaxis.
Drug allergies.
What are common symptoms of allergic rhinitis?
Sneezing, nasal congestion, rhinorrhoea, itchy eyes, postnasal drip.
How does food allergy typically present?
Immediate symptoms like urticaria, angioedema, nausea, vomiting, and anaphylaxis.
In anaphylaxis, the most severe symptom is __________, which can be fatal if untreated.
airway obstruction
What tests are used to diagnose allergic disorders?
Skin prick testing.
Serum IgE levels (RAST test).
Oral food challenge (under supervision).
Spirometry (if asthma is suspected).
How does skin prick testing work?
A small amount of allergen is introduced into the skin, and a positive reaction causes a wheal-and-flare response.
When is a serum IgE test used instead of skin prick testing?
When skin testing is contraindicated (e.g., severe eczema, antihistamine use).
What are the general principles of allergic disorder management?
Allergen avoidance.
Symptomatic treatment (antihistamines, corticosteroids).
Emergency management (epinephrine for anaphylaxis).
Immunotherapy (desensitisation).
What is the first-line treatment for allergic rhinitis?
Intranasal corticosteroids (e.g., fluticasone).
How are food allergies managed?
Strict avoidance of the allergen.
Emergency epinephrine (EpiPen) for anaphylaxis.
What is immunotherapy and when is it used?
A long-term treatment that desensitizes the immune system to allergens, used for severe allergic rhinitis or venom allergies.
What are possible complications of allergic disorders?
Anaphylaxis (life-threatening).
Asthma exacerbation.
Chronic sinusitis (in allergic rhinitis).
Severe eczema.
What is Anaphylaxis?
Anaphylaxis is a life-threatening medical emergency. It is caused by a severe type 1 hypersensitivity reaction. Immunoglobulin E (IgE) stimulates mast cells to rapidly release histamine and other pro-inflammatory chemicals. This is called mast cell degranulation. This causes a rapid onset of symptoms, with airway, breathing and/or circulation compromise. Anaphylaxis marks the most extreme endpoint of the spectrum of allergy. It is defined as a “serious systemic hypersensitivity reaction that is usually rapid in onset and may lead to death if not recognised and treated promptly
What is the key feature that differentiates anaphylaxis from a non-anaphylactic allergic reaction?
compromise of the airway, breathing or circulation
Presentation of anaphylaxis?
Patients present with a history of exposure to an allergen (although it can be idiopathic). There will be rapid onset of allergic symptoms:
Urticaria
Itching
Angio-oedema, with swelling around lips and eyes
Abdominal pain
Additional symptoms that indicate anaphylaxis are:
Shortness of breath
Wheeze
Swelling of the larynx, causing stridor
Tachycardia
Lightheadedness
Collapse
3 Medication options in anaphylaxis
Intramuscular adrenalin, repeated after 5 minutes if required
Antihistamines, such as oral chlorphenamine or cetirizine
Steroids, usually intravenous hydrocortisone
Why do all children need to have a period of assessment and observation post-anaphylactic attack?
All children should have a period of assessment and observation after an anaphylactic reaction, as biphasic reactions can occur, meaning they can have a second anaphylactic reaction after successful treatment of the first. Children should be admitted to the paediatric unit for observation.
How do you confirm anaphylaxis?
Anaphylaxis can be confirmed by measuring the serum mast cell tryptase within 6 hours of the event. Tryptase is released during mast cell degranulation and stays in the blood for 6 hours before gradually disappearing.
Examples of Adrenalin Auto-injectors
Epipen, Jext and Emerade are trade names for adrenalin auto-injector devices.
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.
IM Adrenaline Dose for < 6 months
100-150 micrograms (0.1 - 0.15 ml 1 in 1,000)
IM Adrenaline Dose for 6 months- 6 yrs
150 micrograms (0.15 ml 1 in 1,000)
IM Adrenaline Dose for 6-12 year olds
300 micrograms (0.3ml 1 in 1,000)
IM Adrenaline Dose for >12 y/o
500 micrograms (0.5ml 1 in 1,000)
What is the best site for IM injection?
anterolateral aspect of the middle third of the thigh.
