(SciShow intro)
Hank Green: Have you ever noticed that some things that seem... stimulating at first turn out to be eventually irritating? This is pretty much my relationship with the Black Eyed Peas, which is interesting because black-eyed peas go really well with pepper, which is what this episode is about. (0:16)

Pepper is a stimulating substance, but stimulants in the wrong amounts, or at the wrong times, or in the wrong places, can be super irritating. People today know black and white pepper as spices, but for thousands of years they were used for their medical properties. That's because one of the active ingredients in this fruit of the pepper vine is an alkaloid called piperine.

Piperine is what gives pepper its bite, and its been found to have antioxidant properties, to stimulate production of digestive enzymes in the pancreas, and stoke the production of other enzymes in the liver that allow your body to metabolize some medications more efficiently. But you don't want it up your nose, because despite some of its health benefits, pepper is also synonymous with sneezing.

Sneezing is an involuntary reflex, the aim of which is to get irritants out of your nose, and piperine, as a stimulant, is especially irritating when it comes in contact with your nose's mucus membranes. That's because it activates your pain and acidity receptors. When piperine is sensed in small amounts, as a taste or smell, those receptors allow you to sense pepper as just bitter or sharp. (1:12)

But if it's actually in your nose, which by the way it should never be, then it'll trigger such a strong sensory response that your involuntary reflexes will totally freak out and try to get it out of there. And that then leads to involuntary sneezing, which, in case you're wondering, is known to scientists as sternutation.
So that's why pepper makes you sneeze, and also why you should stop putting food up your nose.

Thank you to our followers on Tumblr who asked this question and thank you to our Patreon patrons who keep these answers coming. If you'd like to submit questions to be answered or get these Quick Questions a few days before everybody else, you can go to Patreon.com/SciShow to find out how you can become a SciShow Patreon patron.
(SciShow theme music plays)