Food allergies are hypersensitivity reactions to allergens contained in food. They are the most common cause of anaphylaxis-related emergency admissions. Young children are commonly affected, usually beginning in the first two years of life. IgE-mediated reactions are the most common type and have an onset within minutes after ingestion. Clinical features include urticaria, angioedema, wheezing, rhinitis, and abdominal pain. Food intolerance on the other hand does not result in an immune reaction and usually only causes abdominal discomfort. A thorough patient history followed by a skin prick test or radioallergosorbent test (RAST) usually confirm the suspected allergen. Management includes desensitization, avoidance of triggers, treatment of symptoms, and, in the event of anaphylaxis, administration of epinephrine.
- Most common cause of anaphylaxis-related emergency admissions
- 5% of adults, 8% of children
- Sex: ♂ > ♀ in children; ♀ > ♂ in adults
- Age of onset: first and second year of life
Epidemiological data refers to the US, unless otherwise specified.
- against select ingredients in food
- The most common food allergens are cow's milk, eggs, nuts, peanuts , seafood (e.g., shellfish, fish), soy, wheat, fruits (e.g., kiwi)
- Commonly IgE-mediated: (immediate onset; within minutes to 2 hours of ingestion)
- Mixed IgE/non-IgE-mediated and non-IgE-mediated reactions are also possible (delayed onset; hours to days after ingestion)
- Skin: (most common): pruritus, ; , exanthem, ,
- Respiratory: rhinitis (often with sneezing), nasal congestion, dyspnea, wheezing, laryngeal edema
- Gastrointestinal tract: oral allergy syndrome (oral pruritus, tingling numbness, and swelling of the lips, tongue, palate, and throat) , nausea, vomiting, abdominal pain, diarrhea
- Cardiovascular: hypotension, tachycardia, dysrhythmias
- CNS: headache
Respiratory manifestations can be fatal!
- Patient history: determine type of food, time and amount of ingestion, and the type of reaction
- Suspected IgE-mediated reaction
- If above tests are inconclusive or suspected food is not a common allergen
- Elimination diet
- Oral food challenge: the effect of potential allergens on the mucous membranes is tested (the patient is given different foods that contain potential allergens to chew but not swallow in increasing doses over a fixed period of time). May be implemented after a positive elimination diet.
- Clinical features
- Diagnosis: crying that lasts ≥ 3 hours per day, ≥ 3 days per week, for ≥ 3 weeks in an otherwise healthy infant <3 months
- Trial of various feeding and soothing techniques
If blood appears in stools, further examination is necessary, as it is likely that a more serious condition (e.g., intussusception) is involved!
The differential diagnoses listed here are not exhaustive.
- Avoid allergens; and, in case of emergency, treat anaphylactic reactions (see )
- Oral immunotherapy is a novel approach, that is still being studied and not widely available
- The majority of children with milk and egg allergies will outgrow them by 5 years of age.
- A lot of children with food allergies will develop asthma and allergic rhinitis.
- Adult-onset food allergies usually remain for life.