Scientists begin to untangle mechanism that causes IBS

Early work shows how antihistamines could be used to treat the condition

There are thought to be millions of people in the UK with irritable bowel syndrome (IBS), yet despite the large number of sufferers, little is known about the condition. According to the NHS, IBS is usually a lifelong problem and has no known cure, though changes in diet and some medicines can alleviate symptoms.

Now, a team of researchers at KU Leuven in Belgium have uncovered a mechanism behind the stomach pain and discomfort felt by IBS sufferers that could lead to potential new treatments using antihistamines.

The team’s previous research demonstrated that blocking histamine – the compound that’s produced by the body’s immune system in response to an allergen – seemed to improve IBS symptoms.

It’s been established that people who have suffered with an gastrointestinal infection (GI) in the past, such as food poisoning, seem to be more likely to go on to suffer from IBS symptoms. The team hypothesised that this could be the consequence of the immune system becoming sensitive to any foods present in the gut when the infection was present. In other words, if some bad oysters gave you food poisoning once, they could then be a trigger for IBS in the future.

To test this, they took a group of mice and gave half of them a GI infection and then fed them all with an egg protein called ovalbumin. A few weeks after the infected mice had recovered, the team once again presented the whole group with the protein. The mice that were previously infected with the bug released histamine in their gut, while those that had not been infected showed no response. The scientists also noticed the activation of mast cells, which produce histamine. The infection had therefore triggered an immune response to the ovalbumin.

The team then went on to inject gluten, wheat, soy and cow’s milk – which are known triggers for IBS – into the intestines of a small group of 12 human patients with IBS and saw a localised release of histamine in the intestine, just as they did with the mice. The researchers have now begun a larger clinical trial to investigate the effect of treating sufferers of IBS using antihistamines.

“This is further proof that the mechanism we have unravelled has clinical relevance. But knowing the mechanism that leads to mast cell activation is crucial, and will lead to novel therapies for these patients,” said Boeckxstaens. “Mast cells release many more compounds and mediators than just histamine, so if you can block the activation of these cells, I believe you will have a much more efficient therapy".

“Unlike an allergic reaction, with IBS the production of histamine was localised within the intestine”