Why did I almost black out after cutting off the tip of my finger?

Your arteries and veins were sending pain signals to your brain.

Hmm. But I’ve hurt worse stubbing my toe.

You likely suffered from what is called vasovagal syncope, most likely triggered by the pain in the finger. It is actually a reflex event, so not one you can “control”. The pain sent a signal to your brain which then quickly signaled the blood vessels in your legs to dilate, leading to pooling of blood in your legs. More blood in the legs means less to the heart and brain. Thus, you “almost passed out”. As you so correctly alluded to, this is also commonly triggered by the sight of blood.

Wow, great answer! Thanks a bunch.

No problem. Don’t forget you should probably get a tetanus shot if you haven’t had one recently… (i.e. in the last 5–10 years) since you were cut by a knife.

Yeah, spent a goof portion of the day in the ER.

yeah, same thing happened to me when i smashed my thumb in a car door and broke the nail open. like you, the blood didnt bother me but i got that sick feeling in my stomach and really light-headed. I sat down and had some cold water and felt much better. Although, when I was rinsing off the blood in the sick the lady turned on the garbage disposal so that might not have helped ;) anyway, she said it had something to do some nerve near your stomach that starts with a v.

@8. You must be referring to the vagus nerve. Thus the term, vasovagal syncope.

ah, thats what it is. Thanks!

because your cool like that…......

I think it happens as a survival mechanism… to get you to stop cutting yourself apart!