Food allergy

Food allergy (Food allergy)

1) Disease description (Causes and symptoms)

• Causes and pathophysiology: The immune system recognizes proteins contained in specific foods as harmful substances and causes a hypersensitivity reaction (including immediate IgE-mediated reactions or non-IgE mechanisms). Due to an excessive immune response, mediators such as histamine are released, causing symptoms involving the skin, respiratory system, digestive system, and vascular system.
• Common trigger foods: Eggs, milk, wheat, soy, peanuts, tree nuts (such as chestnuts), fish, shellfish, etc. (accounting for approximately 90%). Other causes may include sauces, fruits (bananas, melons), soy products, spices, and others.
• Risk factors: Parental history of allergies (approximately 50% if one parent is affected, approximately 70% if both are affected), existing allergic diseases such as atopic dermatitis and asthma, infants and children (due to an immature digestive system), etc.
• Main symptoms: Usually begin within minutes to several tens of minutes after ingestion — hives, erythema, itching, swelling of the lips and area around the mouth, vomiting, diarrhea, abdominal pain, runny nose, tearing and itchy eyes, difficulty breathing, wheezing, chest tightness, dizziness and fainting (tachycardia and hypotension), etc. In severe cases, anaphylaxis (which can be fatal) may occur.

2) Treatment methods

• Basic principle: Identify and thoroughly avoid the causative food (prevention is most important).

• Emergency treatment (priority when anaphylaxis is suspected):

  • Immediate intramuscular injection of epinephrine (into the outer thigh).
    • Adults: 0.3–0.5 mg IM once; may be repeated at 5–15-minute intervals if necessary.
    • Children: 0.01 mg/kg (generally up to 0.3 mg) — refer to the specifications of weight-based auto-injectors.
  • Immediately transfer the patient to the emergency room after administering epinephrine (observation is necessary; a biphasic reaction may occur).

• Adjunctive medications:

  • Antihistamines (to relieve itching and hives), oxygen and bronchodilators (for difficulty breathing), IV fluids and vasopressors (for hypotension), and steroids when necessary (to prevent persistent symptoms and biphasic reactions), etc.

• Diagnostic and preventive treatment:

  • After consultation with an allergy specialist, perform a skin prick test and serum-specific IgE testing.
  • Oral food challenge: The gold standard for confirming the causative food (performed under medical supervision at a healthcare facility).
  • Selective immunotherapy: Oral immunotherapy (OIT) for specific foods (e.g., peanuts) is used for some indications; specialist assessment and an explanation of its advantages and disadvantages are necessary.
  • Patients with severe or recurrent reactions: Prescription of an epinephrine auto-injector and education on its use; medical alert identification (such as a bracelet) is recommended.

• Lifestyle management and precautions:

  • Check food labels and be aware of cross-contamination (processed foods and eating out); for children, share an emergency response plan with childcare facilities and schools.
  • Follow specialist prescriptions for medication treatment according to symptoms.

• Complications: Anaphylaxis (acute respiratory and circulatory failure), secondary infection and nutritional deficiencies (when avoiding a wide range of foods), and biphasic reactions (which may recur within several hours after the initial reaction).

3) Checklist before an outpatient visit (Items to bring and information to confirm)

• Items to bring:
  • List of medications currently being taken (including prescription drugs, OTC medications, and herbal medicines)
  • Previous allergy history (the food eaten when symptoms occurred, amount consumed, time of onset, duration, and treatment received)
  • Previous test results (specific IgE tests, skin tests, previous challenge tests, and emergency room records)
  • Coexisting allergy-related conditions (such as atopic dermatitis and asthma) and family history
  • Records of recent changes in symptoms (photos, symptom diary, etc.)
• Examples of questions to prepare for the outpatient visit (to help with the consultation):
  • A note organizing the ingredient lists and consumption scenarios of foods eaten when recent symptoms occurred
  • Records of medications administered in an emergency (whether epinephrine was used)

4) Examples of general questions to ask the doctor

• "How can I identify the exact food ingredient that caused my symptoms?"
• "Should I be prescribed an epinephrine auto-injector for emergencies? Do I need to learn how to use it in person?"
• "Which foods and precautions must I strictly follow in daily life?"
• "What is the prognosis after treatment, and how likely is recurrence?"

5) Examples of condition-specific questions

• "Can testing specifically identify which component (protein) of the food I ate that caused symptoms was responsible? (Which of the skin test, specific IgE test, or oral food challenge is necessary?)"
• "Could oral immunotherapy (OIT) be considered for peanuts (or a specific food)? What are the indications, benefits, and risks?"

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Note: As diagnosis and treatment vary depending on the individual’s condition, it is safest to consult an allergy specialist and establish a testing and treatment plan.