What is the treatment for scombroid poisoning?

Treatment of Scombroid Poisoning

The first-line treatment for scombroid poisoning is H1 antihistamines, which should be administered promptly to counteract the histamine-mediated symptoms. While scombroid poisoning is often self-limiting, proper treatment can significantly reduce symptom duration and prevent rare complications.

Clinical Presentation and Diagnosis

Scombroid poisoning occurs after consuming spoiled fish (particularly dark-meat varieties like tuna) containing high levels of histamine produced by bacterial decarboxylation of histidine. Key clinical features include:

• Onset within 30 minutes of fish consumption
• Flushing of face and upper trunk (often described as "sunburn-like")
• Urticarial rash
• Headache
• Palpitations
• Nausea, vomiting, abdominal cramps, diarrhea
• Occasionally dizziness and hot flushes

Unlike true fish allergy, scombroid poisoning is a toxin-mediated reaction rather than an immunologic response, though symptoms can appear similar to an allergic reaction 1.

Treatment Algorithm

First-Line Treatment:

1. H1 Antihistamines:
   • Oral antihistamines are the mainstay of treatment 2
   • Options include diphenhydramine, cetirizine, or loratadine
   • For severe cases, parenteral administration (e.g., promethazine) may be required 3

For Moderate to Severe Cases:

1. H2 Antihistamines:

   • Can be added as adjunctive therapy (e.g., ranitidine) 4

2. Corticosteroids:

   • May be administered for more severe symptoms
   • Typically intravenous methylprednisolone for significant reactions 4, 5

For Severe Cases with Hemodynamic Instability:

1. Fluid Resuscitation:

   • Aggressive fluid therapy with crystalloids and colloids may be required for patients with distributive shock 4

2. Vasopressors:

   • For persistent hypotension despite fluid resuscitation
   • Similar approach as used in anaphylaxis management 1

Monitoring:

• Most cases resolve within 6-12 hours
• Observe for at least 4-6 hours after symptom resolution
• Extended monitoring for patients with severe symptoms or comorbidities

Special Considerations

• Differential Diagnosis: Important to distinguish from true fish allergy to prevent incorrect labeling of patients as allergic to fish species 3

• Carbon Monoxide Exposure: Consider checking carboxyhemoglobin levels if fish was cooked in an enclosed space, as this could represent a concomitant carbon monoxide poisoning requiring hyperbaric oxygen therapy 4

• Confirmation: Diagnosis can be confirmed by measuring histamine levels in the implicated fish or patient's plasma, though treatment should not be delayed pending these results 5

Treatment Pitfalls to Avoid

• Misdiagnosis as fish allergy: Scombroid poisoning is a toxin-mediated reaction, not an allergic response 3, 6

• Delayed treatment: Prompt administration of antihistamines is essential to reduce symptom duration

• Inadequate monitoring: Though usually benign, rare cases can develop significant cardiovascular complications requiring more aggressive management 4

• Failure to report: Health authorities should be notified to prevent further cases from the same source 6

Most patients with scombroid poisoning respond well to antihistamines with complete resolution within 24 hours, though severe cases may require more aggressive intervention with parenteral medications and fluid resuscitation.