Question: how to know if you're allergic to fish?
Answer: Hives or a skin rash. Nausea, stomach cramps, indigestion, vomiting and/or diarrhea. Stuffy or runny nose and/or sneezing. Headaches. Asthma. Anaphylaxis (less common), a potentially life-threatening reaction that impairs breathing and can cause the body to go into shock.