Food Allergy Flashcards
Cross reactivity between peanut and tree nuts
33%
Some guidelines say 25-50%
What is the likelihood of peanut allergy in a twin sibling
64%
What is the increased risk if a parent or sibling has peanut allergy
7 fold
Which child has increased allergy risk
First child (decreasing birth order)
Name the 4 animal proteins
- Tropomyosins - crustacean and mollusks
- Parvalbumins/E-F hand proteins - vertebrae fish and frogs
- Caseins - milk
- Minor families - ovomucoid, oligosaccarides, transferrins, serpins, lipocalins.
Name the 4 plant proteins
- Prolamin- seeds, tree nuts, legumes
- Cupin - seed storage globulin in legumes, nuts and seeds
- Bet v 1 - Apple, pear, stone fruit, celery, carrot, soybean, peanut
Cross reactive milk with cows milk
Sheep and goat
Cross reactive foods with latex
Banana, avocado, chestnut, kiwi, potatoe, green pepper
The risk of reactions to kiwi, banana or avocado in Latex allergic people is 11%
The risk of latex allergy amount kiwi-banana- avocado allergic people is 35%
What percentage of beef allergic children reactive to cows milk?
75%
Name your differential for food allergies
- Immune mediated - IgE, FPIES, EGE, atopic dermatitis
- None immune - metabolic (lactose intolerance), toxic (scromboid), undefined (Sulfites)
- Other - Frey’s syndrome (auriculotemporal syndrome causing flush in facial nerve distribution), gustatory flushing, irritant reactions, infections
What is the Predictive SPT threshold for peanuts
Wheal size of 8 mm or greater was high predictive of having a positive food challenge (PPV 95%)
Which peanut component is associated with birch cross reactivity
Ara H8
Which peanut component has highest diagnostic accuracy
Ara H2
Can the results of the diagnostic test be used to predict the severity of a future allergic reaction?
No, the clinic should not use the result of the SPT or sIgE to whole peanut or the components to determine the severity of an allergy phenotype or to predict the severity of a future reaction
Name the Special circumstances for screening infants who present with food allergy
Special cases may be made for screening infants who present with egg allergy and severe atopic dermatitis in the first 4-6 months of life that is poorly controlled despite escalating care
NIAID did recommend strong consideration that either peanut spt or sIgE be obtained and interpreted before early peanut introduction in these infants.
There is no role for component testing for screening
Should children with a family history of peanut allergy in another sibling be evaluated for peanut allergy prior to being introduced?
Screen, but for siblings for peanuts allergy should not be routinely performed.
However, there is consideration for a role for testing when patently are overly anxious about introducing peanut and will not introduce peanut through other means
Are all patients with detectable ara h2 clinically allergic to peanuts?
No. Detectable isolated sensitization to ara h2 is not diagnostic for peanut allergy, and a diagnosis can only be made where the individual is sensitized in the context of a known or suspected reaction after eating peanut
Does component testing predict severity
No. No test including components has good sensitivity or specificity to indicate the severity of symptoms of a future reaction.
When should components be ordered?
The role of component testing is evolving and it is unclear how and when these tests should be used.
Ara h2 compared to peanut SPT does have higher specificity, however there is a knowledge gap on whether this should be the first test
95% PPV for egg testing
7 mm
SIgE >7
95% PPV for cows milk testing
> /= 8 mm
SIgE >15
Or >5 if age <1
95% PPV for peanut testing
Spt >/= 8 mm
SIgE >14
95% PPV for fish
SIgE >/= 20
Natural course of milk, egg, wheat and soy
40% by age 8 for milk, 80% by age 16
68% egg allergy resolved by age 16
Risk factor for death
- Underlying asthma
- Delayed epinephrine
- Symptom denial
- Teens
Predictors of future tolerance
- Lower early SIgE
- Reduction in SIgE over time
- Reduction in spt wheal size
- Lower atopic dermatitis severity
- Decreased igE epitope diversity and lower igE binding affinity
6 ways to prevent food allergy
- Do not restrict maternal diet in pregnancy or lactation
- For patients at risk for developing food allergy use partially or extensive hydrolyzed formulas if they are not breast fed
- Encourage breast feeding for 4-6 months
- Do not introduce soldiers until 4-6 months
- Do not routinely recommend probiotics or prebiotic
- Do not try and prevent food allergy but substituting with soy formula/milk
Name 8 resources for families with food allergy
- CSACI
- AAAAI
- ACAAI
- WAO
- CAAIF
- Food allergy network canada
- food allergy and anaphylaxis alliance
- allergy and asthma information association
mechanism of flushing with alcohol
- etoh causes vasodilation of blood vessels in the skin due to alcohol and its metabolite acetylaldehyde
- niacin contains nicotinic acid which leads to flushing bc of increase in prostaglandin which is a potent vasodilator
risk factors for food allergy
- first degree relative with food allergy
- decreasing birth order (first child greatest risk)
- born in autumn or winter
- severe eczema and egg allergy linked to peanut sensitization
RFs for death in food allergy
- severe uncontrolled asthma
- symptom denial/ previous severe reaction
- adolescents and young adults
- increased PAF
what sIge egg cut off would stop you from a baked challenge?
sIgE of 11
what is the sensitizing agent in alpha gal
lone star tick aka amblyomma americanum
what is heiner syndrome?
- food induce pulmonary hemosiderosis
- most often associated with a non IgE mediated hypersensitivity to milk
- IgG abs to cows milk are seen and needed for dx
- presented with recurrent pneumonia, infiltrates, hemorrhages and GI blood loss
CI to OFC
- High likelihood of reacting to the food based on history, skin testing, or sIgE
- Recent reaction in the past 6-12 months
- Relatively contraindicated in patients with high risk of severe anaphylaxis
- Recent convincing reaction in the past 6-12 months
- Unstable asthma
- Conditions that may affect resuscitation – CV disease, β-blocker use, difficult vascular access
- Food is frequently implicated in fatal and near fatal anaphylaxis
- Peanuts, tree nuts, fish, shellfish, seeds
How to oral vaccines work?
Oral viral vaccines may work by infecting dendritic cells in the gut and stimulate a strong innate immune response that promotes T and B cell activation
Two types of immunoassays
Two main types:
- Particle methods
- Precipitation of immune complexes (electrophoresis)
- Measurement of light scattering by immune complexes in solution (turbidimetry and nephelometry) - Label methods
- Uses label on antigen or antibody to identify complex formation
what is gel electrophoresis
- SPEP, Cryoglobulins, Quantitative immunoglobulins
- Separates molecules based on their size and charge
- Proteins are cleaved and loaded into wells in a gel
- An electric current is passed through the chamber and proteins move towards the positive cathode
- Separate out by weight and charge
what is nephlemetry
- Measures light scatter from serum and compares to amount of scatter from known mixtures
- Used to determine concentration of individual serum proteins (e.g. hemoglobin, haptoglobin, complement, CRP, RF)
most common foods in EIA
wheat and celery
