Hello. Thank you for asking at HCM. I went through your history. As you are not experiencing symptoms every time you eat fish, first of all I would think of Histamine fish poisoning rather than fish allergy. Histamine fish poisoning is a relatively common type of food poisoning. It occurs after consumption of improperly preserved or inadequately refrigerated fish (Fish require stringent refridgeration for preservation). It occurs due to presence of excess of a substance called histamine in the fish. The symptoms are the ones you described - skin rash, itching, headache, palpitation, sometimes breathlessness, etc. The symptoms develop within a few minutes of consumption of fish and usually subside by 6, rarely last up to 12 hours. A very important thing to know is that it is not possible to know whether the fish is likely to cause histamine poisoning by look or even taste of the fish. It looks and tastes same. Only sometimes one feels a typical peppery or burning taste in mouth while consuming fish, one can suspect it is rich in histamine and one should not consume it. Usually antihistamines medications like chlorpheniramine and ranitidine are used for treatment of symptoms. So, in your case, I would think of Histamine fish poisoning rather fish allergy. It is even more common wish some variety of fish like Tuna, Sardine, Mahi-mahi, etc. It is not an allergy. It usually is benign and self-limited, but rarely it can cause death. If you experience any serious symptom like difficulty in breathing, dizziness, palpitation, etc it is advisable to go to ER and get examined by physician and treated. Hope this will be helpful to you. Wish you the best of the health. Regards.