Food Allergy Flashcards
What is the simple way of classifying adverse reactions to foods (+ some subcategories)?
- Immune-mediated (IgE, non-IgE, and cell-mediated)
- Non-immune mediated (metabolic, pharmacologic, toxic)
Food allergy vs food intolerance
- Allergy is immune-mediated reaction to ingested food, resulting in clinical symptoms
- Intolerance is NOT immune mediated, and does not cause life-threatening reactions like anaphylaxis
What are the most common foods that trigger an allergic reaction?
- Wheat
- Egg
- Peanuts/treenuts
- Dairy
- Fish/other seafood
- Sesame (big bird dying of anaphylaxis)
What are the two peaks of age for food allergies? What gender is more prevalent in each?
- First peak occurs under five years of age (more males)
- Second peak occurs in adolescence/young adulthood (more females in this peak)
Which foods trigger consistent severe reactions across the lifespan? Which allergies are more likely to resolve later in life?
-pea/treenuts, shrimp and fish similar across life in triggering the most severe reactions
- Egg, milk, wheat and soy allergies are more likely to resolve than nut or seafood allergies
True or false: due to the anatomical variation of infant’s airways, we should avoid giving allergenic foodsin early life, since anaphylaxis is harder to treat/more fatal
- False
- Introduction of these foods earlier in life is shown to decrease risk of developing an allergy
What’s the link between childhood eczema and risk of developing food allergies?
- Greatly increased risk of developing allergies (!!!)
- Perhaps due to exposure to allergens through broken skin barrier (without oral exposure)
Low levels of this vitamin in infancy are associated with increased risk of allergies…
Vitamin D
How might early microbial exposure affect allergy development?
- Microbial exposure affects early microbiota
- Microbiota have immune-modulating effects; altered microbiome associated with altered allergy development
Describe the sensitisation phase of a type 1 hypersensitivity reaction
- Initial antigen exposure, presented to naive t helper cell via antigen presenting cell with co-stimulatory molecule
- This antigen (plus surrounding cytokines) triggers the T helper to differentiate into a th2 cell (where else are these?)
- Th2 releases cytokines to trigger B cells to produce IgE antibodies, and increases oesinophil production
- IgE antibodies bind to fc epsilon receptors on mast cells
Describe the reactive phase of a type 1 hypersensitivity reaction
- Secondary (or higher) antigen exposure
- CROSS-LINKING of IgE antibodies on the surface of mast cells triggers an immune response (what is x-linking?)
- Mast cell degranulates, also triggering degranulation of oesinophils (early) and later, the joining of basophils
- Specifically, histamine from mast cells causes bronchoconstriction (difficulty breathing) and increased vascular permeability (urticaria and swelling)
Which interleukins are involved in type 1 hypersensitivity? Which of these cause IgE class switch, and oesinophil recruitment?
- IL4 (B cell class switch)
- IL5 (oesinophil recruitment)
- IL10
List three ways in which adrenaline helps to treat anaphylactic reactions?
- Binds to alpha receptors, inducing vasoconstriction and thus increasing blood pressure
- Bind to beta 1 receptors, increasing cardiac contractility and output, thus aiding heart function
- Binds to beta 2 receptors, inducing bronchodilation and thus counteracting the effects of histamine
