Could vomiting be a shellfish allergy?

Dear Dr. Roach: After a bout of suspected food poisoning about six months ago, I’ve had two incidences of violent vomiting for about a half hour. Both of the preceding two meals included shrimp, which I have eaten often in the past without a problem. The episodes were just a month apart. I was surprised to read that shellfish allergy can develop suddenly in adults. I’m afraid to eat it again, and I’ll follow up with my doctor for an allergy test. — M.C.W.

Allergies to fish and shellfish are common, seen in about 3% in U.S. adults. The symptoms vary among different people affected. Of all the shellfish, shrimp is likeliest to cause an allergy.

The usual allergic reaction to shrimp begins within minutes. The skin may show redness or warmth, itching or hives; people may notice tingling or swelling in the mouth or lips; and severe allergic reactions can cause dizziness, fainting, low blood pressure and confusion. It can sometimes lead to cardiac arrest.

Gastrointestinal symptoms can also occur as an immediate symptom, including severe vomiting, diarrhea and abdominal pain. However, stomach symptoms may also occur as a delayed type of allergic reaction. People often consider this to be “food poisoning” and may not recognize it as an allergy.

Finally, it’s possible that you have had bad luck and have had several episodes of diarrheic shellfish poisoning from contaminated shellfish.

An allergist is the ideal consultant to help sort out whether this really is an allergy. Both blood tests and skin tests may be helpful. I agree with you avoiding shellfish until you get evaluated.

Incidentally, the ability to vomit and have diarrhea is a remarkable strength of the stomach and rest of the digestive system: You want to be able to get rid quickly of contaminated food.