What is the treatment for a rash caused by a peanut allergy?

Treatment for Rash Caused by Peanut Allergy

For a rash caused by peanut allergy, first-line treatment is an H1 antihistamine such as diphenhydramine (1-2 mg/kg, maximum 50 mg), with epinephrine reserved for cases showing signs of anaphylaxis or systemic involvement. 1, 2

Assessment of Severity

Before initiating treatment, quickly assess the severity of the reaction:

Mild Reaction (Isolated Rash)

• Localized urticaria (hives)
• Few hives around mouth or face
• No respiratory or cardiovascular symptoms
• No gastrointestinal symptoms

Severe Reaction/Anaphylaxis (Requires Immediate Action)

• Multiple organ system involvement
• Respiratory symptoms: wheezing, throat tightness, stridor, cough, dyspnea
• Cardiovascular symptoms: hypotension, tachycardia, syncope
• Gastrointestinal symptoms: vomiting, diarrhea, abdominal cramps

Treatment Algorithm

For Isolated Rash (Mild Reaction)

1. H1 Antihistamine:

   • Diphenhydramine 1-2 mg/kg (maximum 50 mg) orally 2
   • Alternative: Cetirizine 2.5-10 mg orally (less sedating) 1

2. Consider adding H2 Antihistamine for better response:

   • Ranitidine 1-2 mg/kg orally 2

3. Monitor for progression of symptoms for at least 2 hours

   • If symptoms worsen or new symptoms develop, escalate treatment

For Anaphylaxis or Severe Reaction

1. Epinephrine (First-line) 1, 2, 3:

   • 0.01 mg/kg IM (1:1000 solution) in mid-outer thigh
   • Maximum dose: 0.5 mg
   • Autoinjector dosing:
     • 10-25 kg: 0.15 mg epinephrine autoinjector

     • 25 kg: 0.3 mg epinephrine autoinjector

   • May repeat every 5-15 minutes if symptoms persist

2. Position patient recumbent with lower extremities elevated if tolerated 2

3. Oxygen 8-10 L/min via face mask for respiratory distress 1

4. IV Fluids for hypotension:

   • Normal saline 20 mL/kg bolus 1

5. Adjunctive Medications:

   • H1 Antihistamine: Diphenhydramine 1-2 mg/kg (max 50 mg) IV/IM/oral 1, 2
   • H2 Antihistamine: Ranitidine 1-2 mg/kg IV/oral 2
   • Corticosteroids: Prednisolone 1 mg/kg orally or Methylprednisolone 1 mg/kg IV 1, 2
   • Bronchodilator (if wheezing): Albuterol nebulization or MDI 1, 2

Follow-up Care

1. Observation period:

   • Mild reactions: 2-4 hours
   • Severe reactions: 4-6 hours minimum, consider 24-hour observation 2

2. Prescription for epinephrine autoinjector for patients with history of severe reactions 2

3. Continuation of medications:

   • H1 antihistamines for 2-3 days
   • Consider short course of oral corticosteroids for moderate-severe reactions 2

4. Referral to allergist for comprehensive evaluation and management plan 2

Important Considerations

• Peanut allergy affects approximately 1.1-2% of the population and is among the most common causes of food-induced anaphylaxis 4, 5

• Skin symptoms occur in 89% of initial reactions to peanuts, but 52% also involve respiratory symptoms and 32% involve gastrointestinal symptoms 6

• Delayed administration of epinephrine in anaphylaxis is associated with poorer outcomes; do not hesitate to use epinephrine for systemic reactions 2

• Accidental exposures to peanuts are common (7-14% annually), with one-third to one-half potentially resulting in anaphylaxis 4, 7

• Many patients with peanut allergy are inadequately treated during reactions, with studies showing only 41% of patients who experienced cardiovascular collapse received epinephrine 7

• Never substitute antihistamines or corticosteroids for epinephrine in cases of anaphylaxis 2