What should I do if I suddenly develop a food intolerance or allergic reaction?

Sudden Food Intolerance or Allergic Reaction: Immediate Action Required

If you suddenly develop symptoms after eating a food—especially respiratory symptoms (wheezing, throat tightness, difficulty breathing), cardiovascular symptoms (dizziness, rapid heartbeat, low blood pressure), or widespread hives—you should immediately administer epinephrine if available and call 911, as this may represent life-threatening anaphylaxis. 1, 2

Recognize the Emergency: Signs of Anaphylaxis

Food-induced anaphylaxis typically develops rapidly within minutes to 2 hours after exposure and can be fatal within 30 minutes to 2 hours. 1 You should suspect anaphylaxis if you experience:

• Skin symptoms (in 80-90% of cases): Flushing, itching, hives, or swelling of lips/tongue/face 1
• Respiratory symptoms (up to 70% of cases): Throat tightness, difficulty swallowing, wheezing, shortness of breath, or choking sensation 1
• Gastrointestinal symptoms (up to 40% of cases): Cramping abdominal pain, nausea, vomiting, or diarrhea 1
• Cardiovascular symptoms (up to 35% of cases): Dizziness, rapid heartbeat, feeling faint, or collapse 1

Critical caveat: 10-20% of anaphylaxis cases have NO skin symptoms, so don't wait for hives if you have respiratory or cardiovascular symptoms. 1

Immediate Treatment Steps

First-Line Emergency Treatment

1. Administer epinephrine immediately if you have respiratory symptoms, cardiovascular symptoms, or multiple body systems involved 1, 2

   • Inject 0.3-0.5 mg (adults) or 0.01 mg/kg (children, max 0.3 mg) of 1:1000 epinephrine intramuscularly into the outer thigh 2
   • Give a second dose after 5-15 minutes if symptoms persist or worsen 3
   • Epinephrine is the ONLY medication proven to prevent death from anaphylaxis 1

2. Call 911 immediately after giving epinephrine—do not attempt to drive yourself 1

3. Lie flat with legs elevated (if tolerated) to prevent dangerous drops in blood pressure 3

What NOT to Do

• Do not rely on antihistamines alone—they are adjunctive only and will not prevent death 1
• Do not delay epinephrine waiting to see if symptoms improve—delayed administration is associated with increased mortality 3
• Do not stand or sit upright if feeling dizzy, as sudden position changes can cause fatal cardiovascular collapse 3

Hospital Observation Period

Even if symptoms resolve after epinephrine, you must go to the emergency department for observation because:

• Biphasic reactions occur in 1-20% of cases, with symptoms recurring up to 8 hours later (rarely up to 72 hours) 1
• Minimum observation period is 4-6 hours after symptom resolution 1, 3
• Longer observation or hospital admission is needed if you had severe symptoms, required multiple epinephrine doses, or have asthma 1

Follow-Up Actions After the Event

Within 24-48 Hours

Report the reaction to your physician immediately while details are fresh in your memory to help identify the specific food trigger. 1

Before Discharge from Emergency Department

You must leave with: 1

1. Two epinephrine auto-injectors (prescription for 2 doses)—one is not enough 1
2. Written anaphylaxis emergency action plan detailing when and how to use epinephrine 1
3. Training on proper auto-injector technique with demonstration and practice 3
4. Referral to an allergist/immunologist for comprehensive evaluation within 1-2 weeks 1

Ongoing Management

• Carry epinephrine at ALL times—compliance is most difficult in adolescents and young adults but is life-saving 1
• Check expiration dates monthly—auto-injectors expire after 1 year and must be replaced 1
• Wear medical alert identification (bracelet/necklace) indicating your food allergy 1

Diagnostic Evaluation by Allergist

Your allergist will use: 1

• Detailed history of the reaction and foods consumed
• Skin prick testing with suspected food allergens (most sensitive test) 1
• Blood tests for food-specific IgE antibodies (less sensitive than skin tests) 1
• Supervised oral food challenge if diagnosis remains unclear—this can be done safely even in patients with prior anaphylaxis, but must be performed in a medical facility prepared to treat reactions 1

Food Avoidance Education

Once the culprit food is identified: 1

• Learn to read food labels meticulously—food allergens can hide in unexpected products 1
• Inquire about ingredients at restaurants—cross-contamination is a real risk 1
• Understand cross-reactive foods (e.g., if allergic to one shellfish, avoid all shellfish) 1
• Educate family, school, and workplace about your allergy and emergency response plan 1

High-Risk Factors for Fatal Reactions

You are at highest risk for death from food anaphylaxis if you have: 1

• Asthma (especially poorly controlled)—the single most important risk factor 1
• History of prior anaphylaxis to the same food 1
• Allergy to peanuts or tree nuts—these cause the most fatal reactions 1
• Adolescent or young adult age—this group has highest mortality due to risk-taking behavior and delayed epinephrine use 1
• Cardiovascular disease (in older adults) 1

If you take beta-blockers, ACE inhibitors, or alpha-blockers, inform your allergist—these medications can worsen anaphylaxis and reduce epinephrine effectiveness. 1

Common Pitfalls to Avoid

• Assuming mild symptoms will stay mild—anaphylaxis can progress rapidly from itchy mouth to life-threatening airway closure 1
• Waiting for "classic" symptoms—not all reactions include hives; respiratory or GI symptoms alone can signal anaphylaxis 1
• Leaving the hospital too soon—late-phase reactions can be just as severe as the initial reaction 1
• Not refilling expired epinephrine—expired medication may not work when you need it 1
• Carrying only one auto-injector—approximately 20% of reactions require a second dose 3