Immunology and allergy Flashcards
What is allergy
An immunological hypersensitivity that can leads to a variety of different diseases via different pathological mechanisms (IgE or non IgE mediated) with different approaches in diagnosis, therapy and prevention
What is the difference between sensitivity and hypersensitivity
sensitivity is normal response to stimulus, hypersensitivity is exaggerated
What is sensitisation?
production of IgE antibodies after repeated exposure to an allergen
What is atopy?
A personal or famillial tendancy to produce IgE in response to exposure to potential allergens. Associates with eczema, asthma, allergic rhinitis and food allergy.
other than food and drug allergy, how may allergy present? (4)
- Insect allergy (local inflammation or anaphylaxis due to bee or wasp sting)
- Allergic rhinitis
- Eczema
- Allergic asthma
- Allergic conjunctivitis
- Urticaria/ hives (macropapular itchy rash due to allergen)
What is the allergic march?
How prevalence of types of allergies change with change with age- Food allergies, asthma and eczema are most common in young but can decrease with age, rhinitis and conjunctivitis tend to affect older ppl more.
What is the difference between food allergy and intolerance?
Intolerance is adverse reactions to food, allergy is immune response
Give 2 mechanisms/ reasons/ examples for food intolerance caused by food characteristics and 2 caused by host characteristics
Food: - pharmacological (caffeine) - Toxic (scromboid fish toxin from spoiled oily fish causes excess histamine production) Host: - metabolic (lactose intolerance) - psychological (food aversion)
Describe the difference in symptoms onset between IgE and non IgE mediated allergy?
IgE mediated: Immediate (5-30 mins)
Non: Delayed (hrs to days)
Describe the common food groups associated with IgE and non IgE mediated allergy?
IgE mediated: milk, eggs, peanuts, tree nuts, fish and shellfish, fruit and vegetables (PFS).
Non: Milk and soya, wheat, rice and oats
Describe the age of onset and resolution of IgE and non IgE mediated allergy?
IgE mediated: onset varies by age of contact. PFS in adolescence and milk by 1 yr. Milk and egg may resolve early, others persist into adulthood.
Non: Most start in infancy and early childhood, all milk by 1 yr. They resolve earlier than IgE, most by school age.
Name and describe the 4 specific disorders that IgE mediated food allergy presents with
- Urticarial/ angiodema: acute hives and swelling w/ N+ V, due to any food
- Anaphylaxis: multiorgan dysfunction w/ cardio and resp symptoms, mainly w/ nuts, fish, milk, egg
- Food associated exercise induced anaphylaxis: food triggers anaphylaxis only if ingestion is followed by exercise within 2 hrs
- Pollen food syndrome (PFS): itching and swelling of lips, mouth, tongue, throat after eating raw veg and nuts- associated with hayfever and unprogressing
State and describe 4 specific presentations of non IgE mediated food allergy?
- protocolitis: bright red blood in stool of otherwise asymptomatic infant (usually milk allergy)
- enterocolitis: feed refusal, vomiting, loose stools, abdo cramps, constipation (usually due to milk, eggs, wheat allergy)
- eosinophillic oesphagitis: reflux symptoms, dysphagia, food impaction, usually due to milk, eggs, wheat
- Food induced enterocolitis syndrome (FPIES): infants with profuse vomiting followed by pallor, lethargy, shock etc. often mistaken for infection but due to milk, soya, rice, wheat, meat
Why does food pollen syndrome occur?
It occurs due to cross reactivity of veg/ fruit pollen and hayfever pollens. The allergen is generally denatured in the stomach, preventing systemic symptoms
Why is milk in baked biscuits or boiled eggs less likely to cause an allergic response than cold milk or raw eggs (eg in mayo) in milk and egg allergies respectively? wordy
heat denatures the proteins to make them less allergenic
