Symptoms of shellfish or seafood allergies include abdominal pain, diarrhea, vomiting and nausea, according to Healthline. Other symptoms include a tingling sensation in the mouth, trouble breathing, congestion, hives or itching, and fainting or lightheadedness. The lips, tongue, face, throat, hands and ears may also swell.
Serious shellfish allergies may cause anaphylaxis, which is a medical emergency, notes Healthline. Symptoms of anaphylaxis caused by shellfish exposure or consumption include a lump in the throat or a swollen throat that causes breathing difficulties, rapid pulse, and extreme dizziness. The person may also experience a marked drop in blood pressure. Doctors recommend that people with shellfish allergies keep injectable epinephrine pens on hand to counteract symptoms.