Science doesn't yet have an indisputable answer to that question.
But a report in July's American Journal of Gastroenterology may provide more insight.
IBS is a functional condition of the intestine.
While no one fully understands what causes IBS, it is not an anatomic problem.
According to the American Academy of Gastroenterology, IBS patients have changes in bowel habits, such as constipation or diarrhea.
They also have abdominal pain along with other symptoms including abdominal bloating and rectal urgency with diarrhea.
Researchers tested 16 common foods on blood from 132 IBS patients and 43 people without IBS.
IBS patients had higher levels of an antibody called IgG4 in response to five foods, compared with those without IBS.
Those five foods were wheat, beef, lamb, pork, and soybeans.
IgG is the major antibody in the body; another antibody called IgE is normally present in only trace amounts, but it is responsible for the symptoms of allergy.
They included Sameer Zar, MRCP, of St. Georges Hospital Medical School in London.
Between one-fifth and two-thirds of IBS patients attribute their symptoms to food hypersensitivity.
By comparison, only about 5 percent of the general population claims food hypersensitivity.
Zar's study included 52 people with diarrhea-prominent IBS, 32 with constipation-prominent IBS, and 24 with alternating IBS.
Those with diarrhea-prominent IBS had markedly higher levels of the antibody IgG4 for wheat, beef, pork, and soybean.
Skin prick tests were done on a smaller group of participants -- 56 with IBS and five without IBS.
A skin prick test places a small amount of substance that triggers an allergic reaction into the skin.
The skin test results didn't sync up with results from the blood antibody tests, write the researchers.
Read WebMD's "Newly Diagnosed with Irritable Bowel Syndrome?