Why does our anus have receptors for spicy stuff?


Why does our anus have receptors for spicy stuff?

In: Biology


The TRPV1 is the receptor that capsaicin (spicy) binds to. It exists all over your digestive tract and nervous system. Your rectum and anus are included in this. These receptors are designed to detect “heat” to keep you safe. But they can get confused with foods that taste “hot.” They cause a reaction to cool you down, and you have a response that says, “No, this is dangerous.”

So you sweat, and blood flow increases, causing redness. These receptors exist in all of your digestive tract, which is why you may experience stomach pains or some cramps after eating this. Not all of it digested and so the response is activated again at the anus.

Its just heat receptors but the skin around the anus is not skin, its membrane, it absorbs chemicals easily, the remaining spice is absorbed and the capsaicin does its trick, fooling you into thinking its hot when its not.

If anything i can feel spice in my intestines as its very uncomfortable and i get diarrhea from it.

There is no specific receptor for “spicy stuff”. At least that is not the intended purpose of it. The nerve endings that get activated by the capsaicin molecule are the same that transmit signals about heat/pain. So as long as there are those nerve endings, and they can be hit by the molecule, which works best on mucosa, then you can feel the spicy stuff. As for the reason why those nerve endings in the anus exist in the first place, this is more difficult to answer. I do not agree with the other answer that it does not serve any purpose. But I must admit that I can not see an obvious one either. It may just be for protection. This is the main reason why pain receptors exist. So damage is avoided.


Cool answers. Now, is there anything that can be done to mitigate this fiery nightmare, once the food is down the hatch?

You think it’s only the butthole and a mouth? Rub a hot pepper on your palm, hand or anywhere else, apply bit of heat (sun, hairdryer), moisture and wait. You will be surprised.

It’s not just your anus – it’s your entire skin too. And this receptor isn’t really for detecting spicy stuff – it’s actually to detect heat (i.e. high temperature). Your skin has heat receptors to prevent damage, so that you can quickly move away from something hot (e.g. pull away your hand) before it burns you (too badly). For some reason, these heat receptors (at least some of them) are also chemically sensitive to a molecule that’s present in spicy foods like chili peppers (specifically the *capsaicin* molecule).

So the reason the anus has these receptors is because your entire skin has them. Only, your anus isn’t protected by an outer, tougher layer, like say the skin on your arms, and so your anus is generally more sensitive. But if you rub a hot chili pepper on your arm you’ll feel it burning too.

In addition to being more sensitive, the reason the anus may stand out as “uniquely” sensitive to spicy food (or the remains thereof) is that these receptors don’t exist in your intestines. So you don’t feel that extra spicy Thai Curry going through your guts, but only when you poop it out as it suddenly hits those pesky receptors again, making it seem like your anus is the culprit, when arguably it’s more the absence of these receptors in your gut that is causing this surprising sensation (basically, just be happy it doesn’t burn the whole time).

“Why” is always a tricky question when it comes to evolution, sometimes the question implies a backwards chain of events. This is sometimes referred to as a “fallacy of teleologic reasoning”. Evolution does not necessarily move towards a goal, and asking “why?” can falsely imply it does.

Also, there’s a chicken and the egg thing happening here, and turning it around makes more sense. Meaning, it’s probably not that there were spicy peppers around, and humans had selective pressure that led people with burning assholes to have fitter offspring. Rather, certain plants selected for bright colors and capcaisin, because it happened to trigger burning in mammalian nervous systems, which kept predators away. Then, humans cultivated those plants for use as spices, causing further selective pressure.

It doesn’t. The receptors “for spicy stuff” are your body’s regular detectors / receptors for actual literal temperature. Your whole skin is covered in them, and so is your digestive tract (including mouth, anus).

Capsaicin (the spicy chemical) is not a “flavour” that activates taste receptors. It activates your temperature receptors. “Hot” food feels “hot” because your brain is getting the exact same signal from temp receptors as if touching something physically hot. (That’s also why hot temp stacks with spiciness and they make each other worse, just activating more of the same receptors.)

It’s important for your mouth to know the temp of things (because cold water is safer to drink, too-hot food would burn your insides, etc), and capsaicin developed to hack this pathway and get felt as “hot”. So spicy food feels hot anywhere you have temp receptors. If you’ve eaten really hot wings or something, you know it’s not just your mouth and anus, the hot sauce will burn on your lips, face skin, anywhere it gets.