History and exam
Key diagnostic factors
common
presence of risk factors
Strong risk factors include a family member with atopic disease and prior atopic dermatitis.
milk, egg, nut, fish, shellfish, wheat, or soya ingestion
Ninety percent of reactions are caused by milk, egg, peanut, tree nuts, wheat, soya, fish, and shellfish in children, and by peanut, tree nuts, shellfish, fish, and vegetables in adults.[1][38][39] All foods ingested before a reaction should be noted, including hidden ingredients found in salad dressings, desserts, sauces, or beverages.
reproducible symptoms
Reaction with every ingestion, although there may be differences based on the amount ingested.
flushing, urticaria, or angio-oedema of the skin
Result of immunoglobulin E-mediated reactions.
sneezing, rhinorrhoea, or nasal congestion
Most often seen in conjunction with other organ system involvement.
Rarely the only presenting sign of food allergy.
dyspnoea, tachypnoea, wheezing, coughing, or cyanosis
Result of immunoglobulin E-mediated reactions.
hoarseness, stridor, or sense of choking
Cellular mediators released during an allergic reaction trigger inflammatory response.
nausea and vomiting
Minutes to 2 hours after ingestion.
Characteristic of gastrointestinal anaphylaxis. Often accompanied by allergic manifestations in other target organs.
abdominal cramping or bloating
Characteristic of gastrointestinal anaphylaxis. Often accompanied by allergic manifestations in other target organs.
diarrhoea
Minutes to 2 hours after ingestion.
Characteristic of gastrointestinal anaphylaxis.
conjunctival injection or lacrimation
Results from immunoglobulin E-mediated reactions.
periorbital oedema
Results from immunoglobulin E-mediated reactions.
abrupt onset of symptoms
Reaction occurs within seconds to minutes of ingestion, and rarely beyond 2 hours. Symptoms typically resolve within 4 to 12 hours spontaneously or may respond to epinephrine (adrenaline), antihistamines.
reaction caused by small amount of food
Reaction caused by very small amounts of food protein.
presence of other allergic disease
Patients with atopic dermatitis, asthma, and allergic rhinitis are more likely to have a food allergy.
uncommon
laryngeal oedema
Results from immunoglobulin E-mediated reactions.
Other diagnostic factors
common
tachycardia or bradycardia
May be present in severe cases.
uncommon
reaction exacerbated by exercise or exertion
In some patients, allergic reactions to foods may only occur after activity or may worsen with exertion.
alcohol or medication ingestion before reaction
Alcohol or medication ingestion is believed to increase the rate of allergen absorption.
cardiac arrhythmia
May be present in severe cases.
hypotension
May be present in severe cases.
Risk factors
strong
family history of food allergy
atopic dermatitis
One third of children with refractory, moderate to severe atopic dermatitis have IgE-mediated clinical reactivity to food proteins. The prevalence of food allergy in this population is significantly higher than that in the general population.[21] Children with early-onset and severe atopic dermatitis are much more likely to have food allergy.[22]
The National Institute of Allergy and Infectious Diseases notes that infants with severe eczema, egg allergy, or both, are at high risk for the development of peanut allergy.[23]
weak
newborn
Newborns, particularly those genetically predisposed to atopic disease, are considered at an increased risk secondary to the immune system being biased towards an allergic or Th2 response, increased gut permeability, and other aspects of digestive immaturity that may promote sensitisation.[24] Th2 refers to an allergic phenotype and the cytokines released, including interleukin (IL)-4, IL-5, and IL-13, which all promote allergic disease.
perinatal peanut oil exposure
One study showed that children topically exposed to peanut-based oils in the perinatal period had an increased risk of peanut allergy.[25]
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