3.2.1 Food Allergy Flashcards
A 10-year-old boy presents to the clinic complaining of tongue and mouth itching within a few minutes after eating apples. His mother states that he has not experienced these symptoms with other foods, but they occur every time he eats a fresh apple. He denies systemic symptoms, and the oral symptoms resolve within a few minutes. Other than allergic rhinitis (nasal inflammation) in the spring months, he is healthy. Of the following, you are MOST likely to advise his mother that:
A) allergy skin testing to fresh apples probably will have negative results.
B) cooking the apple will not alter its allergenicity.
C) her son should avoid eating all fruits.
D) her son should avoid milk products.
E) her son’s symptoms are related to his allergic rhinitis.
E) her son’s symptoms are related to his allergic rhinitis
You are the ER physician and you give the child epinephrine injectable, followed by the antihistamine diphenhydramine (Benadryl), and some intravenous fluids. The mother asks you how she is supposed to know if the peanut caused the reaction or if it was something else and you tell her:
A. peanuts don’t cause allergic reactions if they are baked in a cookie.
B. who knows, she should have just given him diphenhydramine (Benadryl) and see if he okay.
C. this was a minor allergic reaction and she should just avoid peanuts in the future.
D. this was anaphylaxis, possibly to peanut, the epinephrine injection likely saved his life, but he needs further testing to find out for sure if it was peanut or another ingredient in the cookie.
D. this was anaphylaxis, possibly to peanut, the epinephrine injection likely saved his life, but he needs further testing to find out for sure if it was peanut or another ingredient in the cookie
Test positive to allergen, may not go on to proceed to a clinical disease
Proven by IgE Immunocap testing, skin testing, or oral challenge
Sensitization
Define a clinical food allergy. What differentiates it from sensization?
Sensitized
-Exposure causes reproducible characteristic IgE-mediated symptoms
What is allergenicity?
Potential to cause allergic reactions
Differentiate intolerance from allergy.
Intolerance
§Your body cannot break down the food
§Lactose intolerance (pain, bloating, diarrhea with milk)
§Eat small amounts – do okay
Allergy
§Your body mistakes that food for something harmful leading to an IgE-mediated reaction
§Immune response – localized or systemic reaction
§Can be triggered by eating a microscopic amount or even with touch or inhalation of the particles
Is the presence of an atopic dz, like latex allergy, associated w/ a higher or lower prevalence of food allergy?
Higher
What are some of the most prevalent food allergies in children?
Cow’s milk, Egg, Peanut
What is the most prevalent food allergies in adults?
Crustaceans (Shellfish)
Differentiate the symptoms/complication associated with IgE-mediated from those of non-IgE/cell-mediated?
What some complications associated with IgE-mediated food allergies?
anaphylaxis, urticaria, angioedema, oral allergy syndrome, acute rhinitis, acute asthma
What is the typical chemical moiety of allergens? What are rarely allergens?
Proteins or glycoproteins (generally heat resistant and acid stable)
Rarely: carbohydrates
Describe the sensitization process on a molecular level (start with allergen and end with mast cell).
allergen -> allergen phagocytosed by DC -> allergen presented to allergen specific T cell -> Th2 -> Release IL-4, IL-5, IL-14 -> B cell stimulation -> Allergen specific IgE production -> IgE binds mast cell via Fc(epsilon)RI
What is released from mast cells during degranulation that causes the symptoms that present in IgE-mediated responses?
Histamines
Leukotrienes
Cytokines
Prostaglandins
PAF
What are some symptoms that people wrongly attribute to IgE-mediated food allergys?
Migraines, Behavioral / Developmental disorders, Arthritis, Seizures, Chronic fatigue, Inflammatory bowel disease
Describe these aspects of pollen-food syndrome aka oral allergy syndrome: Clinical features, Epidemiology, Key foods, and Allergens.
Clinical features: rapid onset oral pruritus, rarely progressive
Epidemiology: rhinitis due to prior sensitization to pollen
Key foods: raw fruits and vegetables
Allergens: Profilins (heat labile)
What are some common fruits indicated in latex-food syndrome?
Banana, avocado, kiwi, chestnut but other fruits and nuts have been reported
IgE enhances the expression of what receptor on mast cells and basophils?
FcεR1
In a non-IgE-mediated anaphylaxis, what are some of the substances that could be activating the mast cells and basophils?
Complement anaphylatoxin activation (C3a/C5a), neuropeptide release (substance P), cytotoxic mechanisms, IgG and IgM, immune complexes, T cell activation
What are some non-immunologic activators of mast cells and basophils?
venoms, contrast media, opiates, COX-1 inhibitors, vancomycin, NSAIDs, physical factors: cold or exercise
What is mastocytosis? What mutation is associated with this condition?
Mastocytosis: Increased expression/production of mast cells, which leads to greater risk of IgE and non-IgE dependent anaphylaxis.
A GOF mutation is C-kit, which is transmembrane tyrosine kinase receptor for SCF that is responsible for promoting growth, differentiation, and survival of mast cells
What are some of product classes produced by mast cells?
histamine, proteoglycans, proteases (tryptase), cytokines (IL-4, IL-8, IL-13), ang lipid mediators (leukotriene)
What are the clinical criteria for anaphylaxis?
One out of three – highly likely
§Acute onset with skin, mucosal tissue or both involved AND at least 1 of the following:
§Respiratory compromise
§Hypotension or end organ dysfunction
§2+ of the following rapidly after exposure
§Involvement of the skin-mucosal tissue
§Respiratory compromise
§Hypotension
§Persistent symptoms
§Hypotension after exposure
§Low BP or greater than 30% decrease from baseline
Why are histamine studies not very reliable if patient is currently under an attack? What are the two histamine studies?
Histamine has a very short half-life.
Histamine tests: Plasma histamine and 24 hour urine histamine
Aside from histamine tests, what is another test to determine whether a patient underwent an anaphylactic episode?
Total serum or plasma tryptase (another product released by mast cells)
How long must one wait before performing a sensitization test (skin prick test, inradermal)? Why?
3-4 wks. It allows the local mast cells to rebuild their granules
What type of result is most useful when analyzing an immunocap?
Negative
What is considered negative in a immunocap test? postive?
Negative: class 0
Positive: class 2+
What are some important aspects of managing a food allergy?
Ensure nutritional needs are being met
Education (all surrounding family/friends, etc)
Anaphylaxis Emergency Action Plan
Avoidance is the only effective therapy
What are some factors to consider when deciding whether to to re-challenge an allergy?
§Type of food allergy (IgE vs non-IgE)
§Severity of previous symptoms
§Allergen/Prognosis (cow’s milk vs peanut)
§Age of the child
§Skin prick test/in vitro specific IgE should be negative prior to challenge
§Decline in concentration of food specific-IgE is suggestive of development of tolerance
When should you administer epinephrine to a patient who is undergoing anaphylaxis?
If you think about it, administer it. (Basically, there is never a bad time to administer epinephrine to these patients. Also, the sooner the better b/c epinephrine can actually block mast cell degranulation)
What are the three mechanisms of action of epinephrine?
§α1 adrenergic vasoconstrictors - decreases mucosal edema, prevents hypotension, increased cardiac output,
§β1 adrenergic – increased force and and rate of cardiac contractions
§β2 - bronchodilation, decreased release of mediators from mast cells and basophils
In addition to epinephrine, what are some other medications used in treatment?
§Leukotriene inhibitors
§Bronchodilators
§Steroids
§Antihistamines (H1 and H2) - No H2 if a food allergy b/c it may delay absorption
What are the new guidlines from AAAAI/ACAAI /AAP for withholding food from patients?
There was no convincing evidence for any of these guidelines. Common sense still applies. Don’t give 3 month old peanuts
