Thank you for your question, and I'm sorry that you haven't been feeling well.
You might be describing a few different things. Some people experience something called vasovagal syncope - which means that they faint (or come close to fainting) under certain types of stimuli or stress. And laughing could be included in this group of stimuli. People also often feel a bit dizzy and even nauseated beforehand as well.
If your blood pressure is a bit low this might also have something to do with it as well. If you find that you also feel a bit faint after rising from a seated or lying position, then your BP may be low.
There are a few other things that can cause this as well, and sometimes this happens to people without any identifiable underlying cause.
If it continues, or you notice any other symptoms, or if you really want to know what's going on, then setup an appointment with your physician. They can give you a good exam, check you blood pressure and see if that's a factor, and if necessary, they can also order additional testing. Many of the things that can cause this are not terribly concerning, but sometimes people who have narrowing of the carotid arteries can also initially experience similar symptoms. So be on the lookout, and if anything gets worse (or doesn't improve) then discuss it with your physician.
I hope this helps. Please let me know if you have any further questions - I'm more than happy to try and help.
Take care - Dr. Fay
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