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IBS and the Vasovagal Reflex


Updated July 18, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Do you ever experience symptoms of sweating and feeling like you are going to pass out during an IBS attack? As with many symptoms associated with IBS, this can be frightening and may make you wonder if something is more seriously wrong with you. This discussion of the body's own vasovagal reflex may help to put your fears to rest.

Real Life Examples

The following are all examples of unusual symptoms that readers have reported experiencing during an IBS attack:

"The bad part is that, with the rectal pain, I will begin to have a vagus response: my throat will tighten, I will begin salivating, get hot and sweaty. Then spasms will start in my stomach and I will begin rhythmic heaving with acid reflux. There isn't anything in my stomach, so there is not much to vomit, but on occasions, I will bring up the water or the coffee and bile, I suppose. The spasms are quite violent and when the episode is over, I am completely wasted. Sometimes this sequence happens once, but I have had up to three experiences in a morning. It makes it impossible to leave the house some days!"
"I too have vasovagal response during painful cramping IBS attacks. During extreme attacks I always have tingling, profuse sweating (drenching), light-headedness and get close to passing out. I have never actually passed out however. These symptoms make coping with IBS symptoms a lot more difficult because I am unable to think straight and the pain is beyond belief."
"I have suffered from vasovagal (reflex) since I am a child. It wasn't until I was an adult that it was diagnosed. I do know my triggers and have become more aware of how to avoid passing out. However, in the last few years I also suffer from IBS....I have had three serious occasions where the IBS attack was so severe that I had a vasovagal attack. Each time I was extremely close to passing out.....dizzy, blurred vision, headache, nausea, and a drenching sweat."

Vasovagal Reflex

Why do some IBS sufferers have these symptoms? The most likely explanation is the body's own vasovagal reflex. The reflex stems from our vagus nerve, which is a nerve that travels from our brains to our colons, and contributes to a wide variety of physical functions, including swallowing, speaking, heart rate and digestion.

The vasovagal reflex is a sudden triggering of the vagus nerve. This may occur in response to a variety of factors, including:

  • Fear
  • Emotional stress
  • Gastrointestinal illness
  • Pain
  • Sight of blood
  • Standing for a long time
  • Standing up quickly
  • Trauma

The reflex results in an abrupt dropping of blood pressure and a sudden reduction in heart rate. At its worst, the reflex will result in fainting, as blood flow shifts away from the head and down into the legs. Fainting that is triggered by the vasovagal reflex is called vasovagal syncope.

The Vasovagal Reflex and IBS

Unfortunately, research on any possible relationship between IBS and the vasovagal response appears to be non-existent. If you experience symptoms that you believe are related to vagus nerve stimulation during IBS attacks, you should bring this to the attention of your doctor. If you do not actually experience fainting, your doctor is likely to tell you that this is a benign accompaniment to your bowel movements. If you do experience fainting, your doctor may recommend that this syncope (sometime referred to as defecation syncope) be further investigated. For more information on syncope:

What To Do If This Happens to You

Even if your doctor dismisses your symptoms as benign, you could benefit from following the self-care recommendation for syncope that one do their best to avoid things that trigger the reflex. Of course, one cannot avoid defecating! On the most basic level, make sure that you are getting adequate sleep and that you stay hydrated. While on the toilet, or in between trips, you can cross your legs, keeping the muscles tight, and lower your head toward the floor to help to stabilize your blood pressure.

Since acute emotional stress can be a trigger, it may be of help to work to keep yourself as calm as possible when this is happening. Although such episodes can be scary, you can use calming self-talk to help get yourself through it and reduce any unnecessary panic. Remind yourself that your symptoms will pass and find reassurance in the fact that your doctor has checked you out and ruled out any more serious causes of your symptoms. Although there is no direct evidence that utilizing mind/body practices on a regular basis will also help with vasovagal symptoms, it is typically quite beneficial to engage in activities that lower one's overall stress level. Here you will find some options:

Related Reading from Dr. Bolen, Your IBS Guide:


Kapoor, W., Peterson, J. & Karpf, M. "Defecation Syncope" Archives of Internal Medicine 1986 146:2377-2379.

"NINDS Syncope Information" National Institute of Neurological Disorders and Stroke Accessed October 10, 2011.

van Lieshout, J., et.al. "The Vasovagal Response" Clinical Science 1991 575-586.

DISCLAIMER: The information contained on this site is for educational purposes only and should not be used as a substitute for diagnosis or treatment rendered by a licensed physician. It is essential that you discuss with your doctor any symptoms or medical problems that you may be experiencing.

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