Immunology Flashcards
What is an allergy?
An inappropriate hypersensitivity response to a normally harmless allergen. Can be IgE mediated, or non-IgE mediated.
What is sensitisation?
Production of IgE antibodies after repeated exposure to an stimulus.
What is atopy?
A tendency to produce IgE antibodies in response to ordinary exposure to potential allergens.
What are some conditions you might have if you are “a bit atopic”?
Eczema
Asthma
Rhinitis
Food allergy
What is a food allergy?
An immunologically mediated adverse reaction to food.
How does allergic rhinitis present?
What is it also known as?
Blocked runny nose
Itchy nose
Sneezing
Hay fever
What can trigger allergic rhinitis?
Pollen
Pets
House dust mites
A child is brought to you because of chronic itchy red swollen and watery eyes. What immunological differential might you consider?
Allergic conjunctivitis
What is urticaria?
Hives - acute or chronic maculo-papular pruritic rash.
May or may not have angioedema.
When might a child have urticaria?
After a bee/wasp sting with a moderate reaction.
Other than food, what can children be allergic to?
Insects Latex Drugs House dust mites Animals Moulds Pollen
How does allergy presentation change with age?
Food allergy and eczema present earliest, with a peak in asthma presentation slightly later again, then allergic rhinitis incidence increases with age.
What is the hygiene hypothesis?
Lack of childhood/early exposure to allergens increases susceptibility to allergic disease due to suppression of natural immune system development.
What is the dual-allergen exposure hypothesis?
Early oral exposure to food allergens induce tolerance, but early cutaneous exposure to food proteins leads to sensitisation.
What are the 5 Ds of food allergy prevention?
Dry skin (prevent, manage eczema)
Vitamin D
Diet (early weaning, varied diet)
Dogs and Dribble (sharing microbes is good/hygiene hypothesis)
A 12 week old girl presents with vomiting after feeds, hungry but difficult to feed, irritable, and in pain. She has been formula fed since birth.
What are your differentials?
Milk allergy
GORD
Intestinal obstruction
How do non-IgE mediated allergies to food tend to present?
With GI symptoms and failure to thrive, as well as skin symptoms such as pruritis/eczema.
Presentation tends to be delayed compared to exposure.
What are the most common foods that children can be allergic to?
Milk
Eggs
Peanuts
How is lactose intolerance different to a food allergy?
It is metabolic and non-immune mediated, where as true food allergies are immune mediated.
It is still an adverse food reaction.
Other than lactose intolerance, what other non-immune mediated adverse food reactions can people have?
Pharmacological e.g. to caffeine
Toxic e.g. Scromboid fish poisoning
Psychological (food aversion)
Tell me about scromboid food poisoning.
Foodborne illness from spoiled fish.
Bacteria convert histidine to histamine which is unaffected by cooking.
How does scromboid food poisoning present?
10-30 minutes after ingestion -> facial flushing, sweating, headache, dizziness, nausea.
Later -> facial rash (itchy), urticaria, abdominal cramps, diarrhoea, bronchospasm.
What is the pathophysiology of lactose intolerance?
Lactase enzyme activity decreased so lactose ferments in the gut -> diarrhoea, flatulance, and bloating.
A child presents with suspected food allergy.
How would knowing the onset timing help with diagnosis of type of allergy?
IgE mediated onset is immediate to within half an hour.
Non-IgE mediated is delayed (hours to days)
Which foods are more likely to have a non-IgE mediated allergic reaction?
Milk and soya
Wheat
Oats
Rice
Which foods are more likely to have an IgE mediated allergic reaction?
Milk Eggs Peanuts Tree nuts Fish and shellfish Fruits and vegetables
Define anaphylaxis.
Rapidly progressive, potentially fatal, multiple organ system reaction with respiratory symptoms to an allergen.
What can we do to some foods to make them less allergenic?
How can we use this?
Cook it! Denatures proteins, or binds it to other foods for reduced effect.
Use to gradually expose children to foods they are allergic to, in order to desensitise them.
A 2 year old present with blood in their stool, which is also mucousy. They are otherwise well and has no other symptoms.
What food allergy presentation might you consider here?
Proctocolitis
What is pollen food syndrome?
Food allergy to fresh fruit and vegetables which usually presents in adolescence.
What makes it possible for a milk-allergic person to tolerate baked milk?
Casein is more heat resistant than whey, so high temperatures denature some of the proteins.
Bonds are formed with wheat when baking to reduce availability and allergenicity.
Is a well cooked whole egg more or less allergenic than raw egg?
Much less allergenic when cooked - 70% of egg-allergic can tolerate baked egg.
What forms of fish are less allergenic?
Canned tuna and salmon.
Cooking fish does not reduce allergenicity as fish protein is very stable.