What should I do for an adult with no known medical history experiencing an allergic reaction with dyspnea and rash?

Immediate Management of Allergic Reaction with Shortness of Breath and Rash

Administer intramuscular epinephrine 0.3-0.5 mg (0.01 mg/kg in children, maximum 0.3 mg) into the lateral thigh immediately—this is a life-threatening anaphylactic reaction requiring epinephrine as the only first-line treatment. 1, 2, 3

Recognize This as Anaphylaxis

The combination of shortness of breath (respiratory involvement) plus rash (skin involvement) affecting two organ systems defines anaphylaxis, a potentially fatal systemic allergic reaction. 1, 4, 2

• Anaphylaxis is characterized by: rapid onset of symptoms involving skin (urticaria, angioedema, rash), respiratory tract (dyspnea, wheezing, throat tightness, bronchospasm), and potentially cardiovascular collapse. 1, 4, 5
• The presence of dyspnea with rash indicates at least two organ systems are involved, meeting criteria for severe allergic reaction requiring immediate epinephrine. 1, 2

Immediate Actions (First 5 Minutes)

Step 1: Administer Epinephrine Immediately

• Give 0.3-0.5 mg intramuscular epinephrine (1:1,000 concentration) into the lateral thigh. 1, 6, 3
• In children, dose is 0.01 mg/kg (maximum 0.3 mg). 6, 7
• Epinephrine is life-saving and the only medication proven to reverse all symptoms of anaphylaxis by stabilizing mast cells and preventing progression. 7, 2
• Do not delay epinephrine administration—it should be given as soon as anaphylaxis is suspected, before other interventions. 2, 3, 7

Step 2: Call Emergency Medical Services (911)

• Activate EMS immediately after or while administering epinephrine. 1, 2
• Do not delay EMS activation even if symptoms appear to improve. 1

Step 3: Position the Patient

• Place patient supine (lying flat) with legs elevated unless respiratory distress worsens in this position. 2, 3
• If severe respiratory distress or vomiting, allow patient to sit upright. 3

Secondary Interventions (After Epinephrine)

Only after epinephrine administration, consider adjunct medications: 2, 3

• H1-antihistamine: Diphenhydramine 25-50 mg IV/IM or orally (reduces urticaria and itching but does NOT treat anaphylaxis). 8, 2
• H2-antihistamine: Famotidine or ranitidine (may provide additional benefit for skin symptoms). 1, 2
• Corticosteroids: Prednisone 40-60 mg orally or methylprednisolone 125 mg IV (may prevent biphasic reactions but NOT effective for acute symptoms). 9, 2
• Supplemental oxygen: If available and patient has dyspnea or hypoxemia. 1
• Inhaled beta-2 agonist: Albuterol nebulizer if wheezing persists after epinephrine. 1, 2

Monitoring and Repeat Dosing

• Observe the patient continuously for at least 15 minutes after epinephrine administration. 1
• Repeat epinephrine 0.3-0.5 mg IM every 5-15 minutes if symptoms persist or worsen—18-35% of anaphylaxis cases require a second dose. 1, 2, 3
• Monitor for biphasic reactions (recurrence of symptoms without re-exposure), which can occur 4-12 hours after initial reaction. 2, 3

Critical Pitfalls to Avoid

Common errors that increase mortality: 2, 3, 10

• Delaying epinephrine: Antihistamines and corticosteroids alone are insufficient and dangerous—epinephrine must be first-line. 2, 3, 7
• Using oral/IV epinephrine instead of IM: Intramuscular administration in the lateral thigh provides fastest, most reliable absorption. 3, 7
• Administering epinephrine in wrong location: Avoid deltoid or subcutaneous routes—lateral thigh (vastus lateralis) is the only recommended site. 7
• Discharging too early: Patients require minimum 4-hour observation (up to 12 hours if high-risk features present). 2, 3
• Failing to prescribe epinephrine auto-injector: Only 4.5% of anaphylaxis patients receive discharge prescriptions despite guideline recommendations. 10

Post-Emergency Management

After stabilization and EMS transport: 2, 5

• Document the trigger in medical records if identified (medications, foods, insect stings are most common). 4, 2
• Prescribe two epinephrine auto-injectors (0.3 mg for adults, 0.15 mg for children 15-30 kg) for future reactions. 5, 7
• Refer to allergist/immunologist for trigger identification, allergy testing, and development of emergency action plan. 5, 2
• Provide patient education on allergen avoidance, recognizing early symptoms, and proper auto-injector technique. 5, 2

Special Considerations

• Patients on beta-blockers: May have refractory symptoms requiring glucagon 1-2 mg IV/IM if epinephrine ineffective. 2
• Pregnant patients: Epinephrine is safe and necessary—maternal hypotension poses greater fetal risk than epinephrine. 6
• Cardiovascular disease: Use epinephrine with caution but do NOT withhold—anaphylaxis itself is more dangerous than epinephrine's cardiac effects. 5, 2