Digestive Health Irritable Bowel Syndrome What Triggers the Vagal Response? By Barbara Bolen, PhD twitter Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome. Learn about our editorial process Barbara Bolen, PhD Medically reviewed by Medically reviewed by Robert Burakoff, MD, MPH on January 21, 2020 linkedin Robert Burakoff, MD, MPH, is board-certified in gastroentrology. He is the vice chair for ambulatory services for the department of medicine at Weill Cornell Medical College in New York. Learn about our Medical Review Board Robert Burakoff, MD, MPH on January 21, 2020 Print Table of Contents View All Table of Contents Triggers Symptoms Causes Vasovagal Syncope Treatment The vagal response is an automatic response within our bodies that occurs as a result of stimulation of our vagus nerve. It gets its name from the fact that it involves an interplay between your vagus nerve and your blood vessels. When the vagus nerve is suddenly stimulated, it sets off a chain of events within the body. These changes can result in a wide variety of unpleasant sensations and symptoms. Illustration by Brianna Gilmartin, Verywell The vagal response goes by a variety of names, including: Vasovagal reflexVasovagal responseVasovagal attackVagus reflex Vagal Response Triggers There are a variety of triggers that can set off the vagal response. As you will see, some of these triggers are internal, while others come from the environment: Emotional stressBlood being drawn or the sight of bloodFearGastrointestinal illnessHaving a bowel movementHeatPainStanding for a long timeStanding up quicklyTrauma Symptoms of the Vagal Response Once a vasovagal reflex has been triggered, a variety of physical symptoms may be experienced. These include: Blurred or tunnel visionDizzinessFaintingFeeling warmLight-headednessNauseaRinging in earsSkin feels cold and clammySweatingTurning pale Causes The vagal response involves your central nervous system, peripheral nervous system, and cardiovascular system. When the reflex is triggered it causes an abrupt drop in blood pressure and a sudden reduction in heart rate. The blood vessels in your legs may widen, causing blood to pool in your legs. This can further drop your blood pressure. All of these changes can result in less blood flowing to your brain and trigger sensations that make you feel as if you might faint. At its worst, the reflex can result in an actual brief loss of consciousness, a condition known as vasovagal syncope. It is important to know that experiencing episodes in which you have symptoms caused by a vagal response does not necessarily mean that there is something wrong with you. It is thought that the reflex is universal What varies from person to person is the level of reactivity to triggers, in other words, how strongly you might experience symptoms from the reflex. Although the vagal response can be experienced by a person in fine health, it is always a good idea to let your physician know if this has happened to you. Based on your symptoms and your medical history, your doctor will decide if further investigation is warranted. Vasovagal Syncope No discussion of the vagal response is complete without bringing attention to the term vasovagal syncope. Syncope is the experience of fainting due to a drop in blood pressure and a subsequent decrease in the flow of blood to the brain. Thus vasovagal syncope is a loss of consciousness triggered by a vagal response. Vasovagal syncope can cause a person to pass out and drop to the ground. With syncope, the state of unconsciousness typically only lasts for a couple of minutes. As blood flow returns to the brain, the person will return to a normal state of consciousness. How Your Doctor Should Evaluate Your Syncope What to Do in Vasovagal Episodes A vasovagal episode can be frightening but is usually not a sign of a health emergency. The best thing to do is to lie down for approximately 10 minutes or so. Another option is to lower your head between your knees. Drinking some water may be of help as well. Whatever you do, do not stand up quickly as you put yourself at risk for fainting. If you experience vasovagal symptoms when having a bowel movement, as some people who have irritable bowel syndrome experience, you may want to try to keep yourself relaxed, with your head down and your legs crossed as you sit on the toilet to try to keep your blood pressure steady. You may be able to prevent such episodes by getting good sleep, keeping yourself well-hydrated, and avoiding standing for extended periods of time. Report any incidents to your doctor so they can determine whether it warrants further workup. Was this page helpful? Thanks for your feedback! One of the most challenging aspects of having IBS is trying to figure out what's safe to eat. Our recipe guide makes it easier. Sign up and get yours now! Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Patient education: Syncope (fainting) (Beyond the Basics). Updated March 21, 2019. Aydin MA, Salukhe TV, Wilke I, Willems S. Management and therapy of vasovagal syncope: A review. World J Cardiol. 2010;2(10):308-15. doi:10.4330/wjc.v2.i10.308 National Institute of Neurological Disorders and Stroke. Syncope Information Page. Updated March 27, 2019. Additional Reading "Syncope Information Page" National Institute of Neurological Disorders and Stroke. Raj S, Sheldon R. "Management of Postural Tachycardia Syndrome, Inappropriate Sinus Tachycardia and Vasovagal Syncope" Arrhythmia & Electrophysiology Review 2016;5(2):122-129.