Food Allergy Flashcards
Name 5 non-immunological adverse reactions to foods
- Enzyme deficiency
- Histamine reactions e..g strawberries, salami, tuna, salmon
- Toxicity e.g. scrombotoxin poisoning
- Food sensitive migraine
- Flushing in acne rosacea
Give 2 examples of enzyme deficiencies which give rise to adverse food reactions
Are there any populations who experience these more?
- Lactase deficiency (acquired/inheritied)
- Alcohol dehydrogenase deficieny
- South East Asians experience flushing reaction to alcohol
How are non-immunological food reactions diagnosed and treated?
Diagnosis is clinical
- No validated scientific tests
Management is dietary
What is a food intolerance?
All detrimental reactions to food that are non-IgE mediated
- Explains a range of symptoms in terms of food sensitivities
- Commonest is irritable bowel syndrome-type symptoms
- No validated tests- dietary approach
Describe the early phase allergic reaction
- In allergic individuals, exposure to allergens leads to rapid development of symptoms
- Reactions develops within seconds/minutes of expsosure
- Results from binding of allergens to preformed IgE antibodies on the surface of mast cells and basophils
Describe the events that follow mast cell IgE ligation
- IgE binds its specific allergen
- Cross linking of IgE antibodies by allergen leads to clustering of FcεR1 receptors
- The intracellular portion of the receptor becomes phosphorylated
- The resulting intracellular cascade leads to cellular activation
- Mast cell ‘degranulates’ releasing histamine, tryptase and other preformed mediators
State 5 pharmacological effects of mast cell mediators
Skin/mucus membranes
- Hives: wheal and flare
- Angioedema: swelling
Nose
- discharge, sneezing
Eyes
- Conjunctivitis
Gut
- Oral allergy, vomiting, diarrhoea
Lung
- Wheeze
Describe how degradation of the mast cell can lead to the occlusion of the vocal chords
- Histamine in deeper tissue areas–> swelling
- In vocal chords this can cause airway compromise and stridor (LIFE THREATENING)
How do you approach the management of a type 1 allergy
- Think about the potential triggers
- Carry out a test to confirm e.g. skin prick, serology, challenge
- Identify the risk
- Create an avoidance plan and an emergency plan
What are the GI symptoms of IgE mediated food allergy?
- Nausea, vomiting, diarrhoea
- Oral allergy (itching, tingling, irritation): local allergic symptoms in mouth
What are the cutaneous symptoms of IgE mediated food allergy?
Hives
Angioedema
What are the respiratory and CV symptoms of IgE mediated food allergy?
RESP
- Upper airway symptoms: wheezing, rhinitis
- Lowe airway symptoms:
CV
- Dizziness, collapse due to hypotension
What are the general features of true food allergy`?
- Rapidly follows (consumption of) food
- Generally multi systemic
- Recedes rapidly
- Reproducible
- Only rarely implicates multiple food sources
- (positive testing)
Describe in vivo allegen testing
Test for allergen-specific IgE
- Drops of allergen applied to skin
- Top layer of epidermis is punctured with lancet which allows allergen to contact cutaneous mast cells
- If mast cell are sensitised to the allergen, degranulation produces an itchy wheal and flare response <15minutes
- Requires positive and negative controls for validation
How do you request a RAST/Allergen specific IgE immunoassay
Send a clotted sample to immunology lab
- Ask SPECIFICALLY
“Specific IgE to…”
(Known allergen stick to solid phase, if specific IgE present they bind. Wash. A detection antibody is added which binds to Fc portion of bound IgE)