What is the treatment for a contact dermatitis rash caused by touching a peanut butter cup in an individual with a peanut allergy?

Treatment of Contact Dermatitis from Peanut Butter in Peanut-Allergic Individuals

For a localized contact rash from touching peanut butter in someone with known peanut allergy, immediately wash the affected area with soap and water, apply topical hydrocortisone 2.5% cream up to 3-4 times daily, and administer an oral antihistamine such as cetirizine or loratadine to relieve symptoms. 1

Immediate Management Steps

Decontamination

• Wash the affected skin immediately with liquid soap and water, as this effectively removes peanut allergen (Ara h 1) from skin surfaces 2
• Bar soap and liquid soap both successfully eliminate detectable peanut protein, while plain water alone may leave residual allergen 2
• Antibacterial hand sanitizers are less effective and may leave detectable allergen on the skin 2

Topical Treatment

• Apply hydrocortisone 2.5% cream to the rash 3-4 times daily to reduce local inflammation 1
• This addresses the localized urticarial or dermatitic response that can occur at the contact site 3, 4

Antihistamine Administration

• Give an oral antihistamine (cetirizine or loratadine) to relieve acute allergic symptoms 1, 5
• Antihistamines should be readily available for all food-allergic patients for mild reactions 1

Critical Monitoring Period

Observation Requirements

• Monitor the patient for 30 minutes to several hours after the exposure to ensure symptoms remain localized and do not progress to systemic involvement 1
• Watch specifically for: diffuse hives beyond the contact site, respiratory symptoms (shortness of breath, wheezing), obstructive swelling of tongue or lips, or any circulatory symptoms 1

Reassuring Evidence About Contact Reactions

• In a study of 330 skin contact tests with peanut butter in peanut-allergic children, no child developed a systemic reaction from prolonged topical application, even among those who had systemic reactions during oral challenges 4
• A separate controlled study of 30 highly sensitive peanut-allergic children (median peanut IgE >100 kIU/L) found that none experienced systemic or respiratory reactions from skin contact with peanut butter 6
• When reactions did occur from skin contact, they were limited to local erythema, pruritus, or wheal-and-flare reactions only at the contact site 4, 6

When to Escalate Care

Signs Requiring Epinephrine

• Administer epinephrine immediately and call 911 if any of the following develop: 1
  • Respiratory distress or difficulty breathing
  • Diffuse urticaria spreading beyond the contact area
  • Angioedema involving lips, tongue, or throat
  • Vomiting or abdominal cramping
  • Dizziness or signs of hypotension

Risk Context

• While 66% of peanut-allergic patients report symptoms from direct physical contact with peanut-containing foods, systemic reactions from skin contact alone are extremely rare 7
• The primary risk comes from subsequent transfer to mucous membranes (touching eyes or mouth after contact) or accidental ingestion, not from the dermal contact itself 7

Important Clinical Caveats

Distinguishing Contact from Ingestion

• Ensure no peanut was ingested, as even trace amounts can cause systemic reactions in sensitized individuals 3
• If there is any possibility of ingestion (touching mouth, licking fingers), the monitoring period should be extended and threshold for epinephrine use should be lower 1

Prescription Requirements

• All peanut-allergic patients should have epinephrine autoinjectors prescribed and available, even if this reaction appears mild, as future exposures could be more severe 1
• The unpredictability of allergic reactions necessitates preparedness for anaphylaxis, even though contact reactions are typically localized 3, 4

Cleaning Recommendations

• Clean any contaminated surfaces with common household cleaning agents (not just dishwashing liquid, which may be less effective) to prevent re-exposure 2
• Peanut allergen is relatively easily removed from environmental surfaces with standard cleaning products 2