Food allergy is an adverse immune response to food proteins. Most reactions are from peanut, tree nuts, milk, egg, fish, shellfish, wheat, and soya. Symptoms usually appear within 20 minutes of ingestion and nearly always within 2 hours.
Symptoms and signs may vary from pruritus and mild cutaneous eruption to severe anaphylactic respiratory, gastrointestinal, or cardiovascular (e.g., hypotensive) manifestations.
Epinephrine (adrenaline) given by intramuscular injection is the treatment of choice for severe systemic symptoms (anaphylaxis); lesser reactions are managed with a range of therapies from simple withdrawal of suspected food allergen to oral antihistamines.
Patients should be encouraged to obtain medical identification jewellery, be knowledgeable of the incipient signs and symptoms of an allergic reaction, be trained how to use an epinephrine (adrenaline) auto-injector, and know how to activate emergency response services.
Food allergy is an adverse immune response to food proteins.
Reactions may be either IgE-mediated, non-IgE-mediated, or mixed IgE-mediated/non-IgE-mediated reactions. IgE-mediated reactions to food are primarily considered here.
History and exam
Key diagnostic factors
- presence of risk factors
- milk, egg, nut, fish, shellfish, wheat, or soya ingestion
- reproducible symptoms
- flushing, urticaria, or angio-oedema of the skin
- sneezing, rhinorrhoea, or nasal congestion
- dyspnoea, tachypnoea, wheezing, coughing, or cyanosis
- hoarseness, stridor, or sense of choking
- nausea and vomiting
- abdominal cramping or bloating
- conjunctival injection or lacrimation
- periorbital oedema
- abrupt onset of symptoms
- reaction caused by small amount of food
- presence of other allergic disease
- laryngeal oedema
Other diagnostic factors
- tachycardia or bradycardia
- reaction exacerbated by exercise or exertion
- alcohol or medication ingestion before reaction
- cardiac arrhythmia
- family history of food allergy
- atopic dermatitis
- perinatal peanut oil exposure
1st investigations to order
- in vitro IgE specific immunoassay
- skin prick testing
Investigations to consider
- food challenges
- component-resolved diagnostics
- atopy patch testing
- Atopic dermatitis
- Auriculotemporal syndrome
- BSACI guidelines for the management of egg allergy
- A consensus approach to the primary prevention of food allergy through nutrition: guidance from the American Academy of Allergy, Asthma, and Immunology; American College of Allergy, Asthma, and Immunology; and the Canadian Society for Allergy and Clinical Immunology
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