Why does Botox make me faint, but fillers don't?

Thank you for your question. There could a variety of reasons, however you would need a medical evaluation to determine the possibilities.  In some people the sight of blood or needles can cause a vaso-vagal response, but this is not related directly to Botox. 

There’s no reason attributable to the Botox that would cause this to happen. It’s possible that some subtle anxiety regarding Botox is triggering this. Perhaps it’s simply the anxiety of it possibly happening again. Worrying about fainting is a sure path to more vasovagal events.   Vasovagal responses are interesting. I have patients who are perfectly fine until I use certain medical words or describe something in too much detail. In other words, it often has more to do with your thoughts than with pain.   Rest assured the Botox itself is not the problem. Ask your injector to inject you while somewhat supine. This may help.    Best to you.