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 
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)
- 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
- RAST (radioallergosorbent test)
- Total IgE-antibody serum test
- N-methylhistamine (urine)
- If above tests are inconclusive or suspected food is not a common allergen
- Elimination diet: The suspected allergens are eliminated from the patient diet, while being observed for an improvement in symptoms without the need for medication.
- 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
- Diagnostics: crying that lasts ≥ 3 hours per day, ≥ 3 days per week, for ≥ 3 weeks in an otherwise healthy infant < 3 months
- Soothing techniques
- Trial of various feeding techniques
Food protein-induced allergic proctocolitis of infancy (FPIAP)
- Definition: a type of delayed inflammatory non-IgE-mediated food allergy in young infants that affects the distal colon
- Epidemiology: Incidence is 17% in the US. 
- Clinical features
- Diagnostics: mainly a clinical diagnosis based on patient history and clinical features
- Differential diagnosis: likely if warning signs such as failure to thrive, abdominal distention, or fever are present
- Treatment: removal of offending foods from the infant's diet
- Complications: progression to chronic colitis and/or persistent food allergy (rare)
- Prognosis: FPIAP resolves spontaneously by late infancy in most cases. 
If blood appears in stools, further examination is necessary to rule out serious conditions (e.g., intussusception).
The differential diagnoses listed here are not exhaustive.