Should I administer epinephrine (adrenaline) for hives?

Should You Give Epinephrine for Hives?

No, epinephrine is not indicated for isolated hives alone—but you should give epinephrine immediately if hives occur after exposure to a known allergen that previously caused anaphylaxis, or if hives are accompanied by any respiratory, cardiovascular, or gastrointestinal symptoms. 1

The Critical Distinction: Isolated Urticaria vs. Anaphylaxis

The key clinical decision hinges on whether you're dealing with isolated urticaria or potential anaphylaxis:

When Epinephrine IS Indicated for Hives

Give epinephrine immediately if any of the following apply:

• Hives plus respiratory symptoms (dyspnea, wheeze, stridor, throat tightness, cough) 1
• Hives plus cardiovascular symptoms (hypotension, dizziness, syncope, tachycardia, chest pain) 1
• Hives plus gastrointestinal symptoms (persistent vomiting, crampy abdominal pain) after allergen exposure 1
• Generalized hives after exposure to a known allergen that previously triggered anaphylaxis in that patient (e.g., peanut, tree nuts, shellfish, milk) 1, 2
• Any uncertainty about whether symptoms represent early anaphylaxis—err on the side of giving epinephrine 1

When Epinephrine Is NOT Indicated

Isolated allergen-associated urticaria without systemic symptoms should be distinguished from anaphylaxis and may respond to antihistamines alone. 1 This means hives occurring in isolation, without:

• Known allergen exposure with prior anaphylaxis history
• Any respiratory compromise
• Any cardiovascular symptoms
• Any gastrointestinal symptoms

Why This Matters: The Progression Risk

Even experienced physicians cannot predict at symptom onset whether an episode will remain mild or escalate to life-threatening anaphylaxis within minutes. 1 Critical points:

• Systemic allergic reactions can rapidly progress from mild to life-threatening 1
• Severe respiratory and cardiovascular symptoms can appear suddenly even after hives have disappeared with antihistamine treatment 1
• Delayed epinephrine administration is directly associated with increased hospitalization, hypoxic-ischemic encephalopathy, and death 3
• Fatal anaphylaxis is often associated with failure to inject epinephrine promptly 1

Practical Clinical Algorithm

Step 1: Assess for Anaphylaxis Criteria

Does the patient meet any of these criteria? 1

1. Hives PLUS respiratory OR cardiovascular symptoms (give epinephrine immediately)
2. Two or more systems involved after allergen exposure:
   • Skin (hives, itching, flushing, angioedema)
   • Respiratory (dyspnea, wheeze, stridor)
   • Cardiovascular (hypotension, dizziness, syncope)
   • Gastrointestinal (vomiting, crampy pain)
3. Hypotension after known allergen exposure (give epinephrine immediately)

Step 2: Consider Context

• Known allergen exposure (especially peanut, tree nuts, shellfish, milk, eggs, fish)? 1
• Prior anaphylaxis history to this allergen? 1
• High-risk patient (adolescent, concomitant asthma, especially if poorly controlled)? 1

Step 3: When in Doubt, Give Epinephrine

If unsure whether symptoms represent anaphylaxis versus isolated urticaria, err on the side of caution and inject epinephrine, then observe closely. 1 The risk-benefit ratio strongly favors treatment.

Administration Details When Indicated

Dosing: 1, 3

• Adults and children ≥30 kg: 0.3-0.5 mg IM
• Children <30 kg: 0.01 mg/kg IM (maximum 0.3 mg)

Route and Location: 1, 4

• Intramuscular injection into the mid-outer thigh (vastus lateralis)
• Never inject into buttock, digits, hands, feet, or deltoid
• Can repeat every 5-15 minutes if symptoms persist 1, 3

Post-Administration: 3, 5

• Transfer all patients to emergency department for observation
• Observe minimum 4-6 hours for biphasic reactions
• Place patient supine with legs elevated if tolerated 1

Adjunctive Treatment (Not Substitutes for Epinephrine)

After epinephrine administration, consider: 2, 5

• H1-antihistamine (diphenhydramine 1-2 mg/kg, max 50 mg)
• H2-antihistamine (ranitidine or famotidine)
• Bronchodilator (albuterol) if bronchospasm present
• Supplemental oxygen as needed
• IV fluids if hypotensive

Critical caveat: Antihistamines and bronchodilators are NOT substitutes for epinephrine in anaphylaxis. 1, 2

Common Pitfalls to Avoid

• Relying solely on antihistamines for hives after known allergen exposure with prior anaphylaxis history 1, 3
• Waiting for "severe" symptoms before giving epinephrine—early administration prevents progression 1, 2
• Assuming all hives need epinephrine—isolated urticaria without systemic symptoms or high-risk context can be treated with antihistamines 1
• Fear of epinephrine side effects (transient pallor, tremor, anxiety, palpitations are expected and not dangerous in otherwise healthy individuals) 2, 4
• Incorrect injection site—always use anterolateral thigh, never buttock or deltoid 4

Safety Considerations

There are no absolute contraindications to epinephrine in anaphylaxis. 3 Even patients with heart disease, hypertension, or those on beta-blockers should receive epinephrine in life-threatening situations, though caution is warranted. 4 The presence of sulfite sensitivity (sodium bisulfite in epinephrine formulations) should not preclude use in anaphylaxis. 4