Overview
Definition:
Scombroid poisoning, also known as histamine fish poisoning, is an allergic-like reaction caused by the consumption of improperly stored fish, such as tuna, mackerel, mahi-mahi, and sardines, which have undergone bacterial spoilage and histamine accumulation
Adolescents are susceptible to this condition, presenting with acute symptoms mimicking an allergic reaction.
Epidemiology:
Scombroid poisoning is the most common foodborne illness associated with fish consumption worldwide
While specific incidence data in adolescents is limited, it occurs sporadically and is often underreported due to mild to moderate symptoms and rapid resolution
Geographical distribution is widespread, linked to fish consumption habits.
Clinical Significance:
Prompt recognition and appropriate management of scombroid poisoning in adolescents are crucial to alleviate distressing symptoms, prevent potential complications, and avoid unnecessary diagnostic workups for true allergic reactions
Antihistamines form the cornerstone of symptomatic treatment.
Clinical Presentation
Symptoms:
Rapid onset of symptoms within minutes to 2 hours after ingestion of contaminated fish
Flushing of the face and neck
Urticaria or rash
Pruritus
Headache
Palpitations
Nausea
Vomiting
Diarrhea
Oral burning or metallic taste
Dizziness
Bronchospasm in severe cases.
Signs:
Erythema of the face and upper trunk
Diffuse urticarial rash
Tachycardia
Mild hypotension may occur
Neurological symptoms like headache or dizziness can be present
Wheezing in cases of bronchospasm.
Diagnostic Criteria:
Diagnosis is primarily clinical, based on the characteristic symptoms occurring shortly after consuming suspect fish
There are no specific laboratory tests for scombroid poisoning, but suspicion arises from a compatible history and presentation
Levels of histamine in fish can be elevated, but this is retrospective and not practical for acute diagnosis
Ruling out true IgE-mediated allergic reactions is important.
Diagnostic Approach
History Taking:
Detailed history of fish consumption is paramount
Inquire about the type of fish, its source, storage conditions (refrigeration, cooking), and the timing of symptom onset
Ask about previous fish allergies or similar reactions
Assess for other food intolerances or recent illnesses.
Physical Examination:
A thorough physical examination should focus on vital signs (heart rate, blood pressure, respiratory rate, oxygen saturation)
Assess skin for rash and flushing
Auscultate lungs for wheezing
Evaluate for signs of dehydration if vomiting or diarrhea is significant.
Investigations:
No specific laboratory investigations are typically required for diagnosis in the acute setting
If severe symptoms suggest anaphylaxis or other serious conditions, investigations like complete blood count, electrolytes, renal function tests, and arterial blood gas may be considered
Histamine levels in the leftover fish can be tested retrospectively but are not clinically useful for the patient.
Differential Diagnosis:
True food allergy (IgE-mediated)
other forms of food poisoning (bacterial toxins, viruses)
ciguatera fish poisoning
allergic reactions to other seafood
vasodilation caused by other agents
Scombroid poisoning can be distinguished by its rapid onset after fish consumption and lack of specific IgE antibodies.
Management
Initial Management:
Immediate discontinuation of fish consumption
Assessment of airway, breathing, and circulation (ABCs)
Monitoring of vital signs is essential.
Medical Management:
The primary treatment for scombroid poisoning is with H1 antihistamines
Oral formulations are generally effective for mild to moderate symptoms
Intravenous antihistamines may be used for more severe symptoms or if vomiting prevents oral administration
Examples include: Diphenhydramine (e.g., 1 mg/kg per dose, maximum 50 mg PO or IV, every 4-6 hours as needed for adolescents)
Cetirizine (e.g., 10 mg PO once daily for adolescents >12 years)
Loratadine (e.g., 10 mg PO once daily for adolescents >12 years)
H2 antihistamines (e.g., ranitidine or famotidine) may provide additional relief but are generally considered second-line
In cases of significant bronchospasm, inhaled bronchodilators (e.g., albuterol) may be necessary
For severe anaphylaxis-like reactions, epinephrine may be indicated, though true anaphylaxis is rare in scombroid poisoning.
Surgical Management:
Surgical management is not indicated for scombroid poisoning.
Supportive Care:
Symptomatic relief is key
Encourage hydration, especially if diarrhea or vomiting is present
Antiemetics may be considered if vomiting is severe
Education regarding safe fish handling and storage practices is important for future prevention.
Complications
Early Complications:
Severe bronchospasm leading to respiratory distress
Hypotension and shock in rare, severe cases
Significant gastrointestinal distress.
Late Complications:
Generally, scombroid poisoning is self-limiting and does not have long-term sequelae
Persistent symptoms are uncommon.
Prevention Strategies:
Purchase fish from reputable sources
Ensure proper refrigeration of fish from the point of sale
Consume fish promptly after purchase
Cook fish thoroughly, though cooking does not destroy pre-formed histamine
Proper freezing and thawing methods are crucial
Educate consumers about the risks associated with improperly stored fish.
Prognosis
Factors Affecting Prognosis:
The prognosis for scombroid poisoning is generally excellent
Rapid and complete recovery is expected with appropriate symptomatic management.
Outcomes:
Symptoms typically resolve within 24 hours with antihistamine treatment
Most adolescents experience complete symptom resolution without any lasting effects.
Follow Up:
No specific follow-up is usually required unless symptoms persist or worsen
Patients should be advised to seek medical attention if symptoms do not improve or if new, concerning symptoms develop.
Key Points
Exam Focus:
Scombroid poisoning is a histamine-mediated reaction, not a true allergy
Prompt administration of H1 antihistamines is the mainstay of treatment
Differentiating from true anaphylaxis is crucial.
Clinical Pearls:
Always inquire about fish consumption when presented with an acute onset of rash, flushing, and gastrointestinal symptoms
Remember that even well-cooked fish can cause scombroid poisoning if it was improperly stored before cooking
Dosing of diphenhydramine in adolescents: 1 mg/kg/dose, max 50 mg PO/IV q4-6h.
Common Mistakes:
Over-reliance on epinephrine for symptoms that are solely histamine-mediated
Failure to adequately question about fish consumption
Misdiagnosing scombroid poisoning as a true food allergy, leading to unnecessary dietary restrictions.