The cause of irritable bowel syndrome is currently unknown.

• IBS is thought to result from interplay of abnormal gastrointestinal (GI) tract movements,
• Increased awareness of normal bodily functions, Change in the nervous
• system communication between the brain and the GI tract.
• Abnormal movements of the colon, whether too fast or too slow, are seen in some, but not all, people who have IBS.
• Irritable bowel syndrome has also developed after episodes of gastroenteritis.
• It has been suggested that IBS is caused by dietary allergies or food sensitivities, but this
  has never been proven.
• Symptoms of irritable bowel syndrome may worsen during periods of stress or menses, but these factors are unlikely to be the cause that leads to development of IBS.

Symptoms include

• Abdominal pain or discomfort for at least 12 weeks out of the previous 12 months. These 12 weeks do not have to be consecutive.
• The abdominal pain or discomfort has two of the following three features:–
  a) It is relieved by having a bowel movement.  b) When it starts, there is a change in how often you have a bowel movement.  c) When it starts, there is a change in the form of the stool or the way it looks.
• Certain symptoms must also be present, such as:-   a) a change in frequency of bowel
  movements,  b) a change in appearance of bowel movements, c) feelings of uncontrollable urgency to have a bowel movement,   d) difficulty or inability to pass stool,
  e) mucus in the stool,   f) bloating, 
• Bleeding, fever, weight loss, and persistent severe pain are not symptoms of IBS and may indicate other problems such as inflammation, or rarely, cancer.