Some fish reactions are not true allergies but are caused by histamine buildup in improperly stored fish.
| Feature | Fish Allergy | Scombroid Poisoning |
| Cause | IgE immune reaction to fish proteins | High histamine levels in spoiled fish |
| Symptoms | Hives, anaphylaxis, swelling | Flushing, nausea, headache, palpitations |
| Onset | Minutes to hours | Within 30 minutes |
| Triggers | Any fish species (allergy-dependent) | Tuna, Mahi-Mahi, Mackerel, Sardines |
| Treatment | Epinephrine, antihistamines, strict avoidance | Antihistamines (Benadryl), medical monitoring |
Scombroid poisoning can mimic an allergic reaction but is caused by bacterial spoilage rather than an immune response.