Allergies are not limited to anything, but it sounds like you could have eaten a bad piece of fish (spoiled, not fresh). The symptoms you described could be either. The only way to know is if you eat the same type of fish at another time and have the same reaction, then it is possible that you have an allergy. Symptoms of allergies can be dizziness, lightheadedness, itchiness (especially in the middle of your palms), hives, swelling, itching in your airways, difficulty breathing, your blood pressure could go down (you'll see spots in front of your eyes if you do). You do not necessarily have to have all the symptoms. Carry Benedryl with you in the event that this should happen again. But if it does not, then it's not an allergy. You can read about what is an allergy on this website.