A female asked:
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lately, i've been experiencing dizziness and momentary blackouts from laughing really hard. what can be causing it?

5 doctor answers
Dr. Richard Zimon
58 years experience Internal Medicine
You are: doing what is called a "VALSALVA" ( Like holding your breath and "straining down"...it causes a slowing of your pulse and drop in your blood pressure which can cause FAINTING !!!!!! If I'm correct being AWARE of this could possibly prevent it!! Hope this is helpful Dr Z
Answered on Jun 3, 2020
Dr. Jana Tomsky Corvalan
26 years experience Family Medicine
La k if oxygen or .: If you mouth hard you may be holding breath , lack of oxygen can make you dizzy. Other possibility is “ partial seizure” triggered by laugh. Whatever is situation if persists see your MD. Keep healthy life stifle ( avoid excess alcohol and sleep well . Avoid junk food . Get regular exercise . .
Answered on Mar 11, 2018
Dr. Robert Perlmuter
Specializes in Internal Medicine
Syncope: We call blacking out syncope. There are several different causes of this. Some of these causes can be significant or serious so please see a doctor as soon as possible.
Answered on Mar 6, 2018
Dr. Raja Abusharr
20 years experience Family Medicine
Vagal Response: Hard laughing, like coughing or retching can stimulate the VAGAL NERVE, an important nerve regulating our parasympathetic system. This nerve travels from our brain down to the pelvis can be stimulated through the movement of the diaphragm. Like brakes on a car, it slows heart, lowers blood pressure. Your brain gets a sudden change in blood flow and you feel dizzy. Not dangerous!
Answered on Mar 4, 2018
Dr. Donald Colantino
60 years experience Internal Medicine
Laughing: Forceful and vigorous laughing can lower your blood pressure and slow down your heart rate by restricting blood flow to the heart from peripheral veins. Also, stimulation of the vagus nerve may play a role in your symptoms. I think the mechanism is similar to holding your breath and bearing down which can cause lightheadedness and loss of consciousness.
Answered on Mar 6, 2018

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