# How does Pepto Bismol work? **URL:** \ **Category:** Factual Questions\ **Created:** [October 3, 2005, 1:08am UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506 "2005-10-03T01:08:48Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [October 3, 2005, 1:08am UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/1 "2005-10-03T01:08:48Z")
I figured this would be easy enough to Google, but almost all the links are to WebMD-type indications/side effects pages or to this widely copied note: > [@](#): > > Bismuth has several actions in the gut. It forms a coating over ulcers in the stomach and gut protecting them from stomach acid and allowing them to heal. It also kills bacteria, including those which are now believed to aggravate ulcers. (as at [http://www.netdoctor.co.uk/medicines/100002038.html](http://www.netdoctor.co.uk/medicines/100002038.html) ) Which is fine for stomach ulcers and H. pylori, but what about diarrhea? Is it the bacteria-killing properties that wipes out diarrhea-causing bacteria? Or does it have some other action in the intestines? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [October 3, 2005, 1:23am UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/2 "2005-10-03T01:23:39Z")
According to [Drugs.com](http://www.drugs.com/MMX/Bismuth_Subsalicylate.html): > [@](#): > > Antidiarrheal—Exact mechanism has not been determined. Bismuth subsalicylate may exert its antidiarrheal action not only by stimulating absorption of fluid and electrolytes across the intestinal wall (antisecretory action) but also, when hydrolyzed to salicylic acid, by inhibiting synthesis of a prostaglandin responsible for intestinal inflammation and hypermotility. In addition, bismuth subsalicylate binds toxins produced by Escherichia coli . Both bismuth subsalicylate and the intestinal reaction products, bismuth oxychloride and bismuth hydroxide, are believed to have bactericidal action. ---
**Author:** ![Amazon\_Floozy\_Goddess](https://avatars.discourse-cdn.com/v4/letter/a/779978/32.png) [@Amazon\_Floozy\_Goddess](https://boards.straightdope.com/u/Amazon_Floozy_Goddess)\ **Post date:** [October 3, 2005, 5:27am UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/3 "2005-10-03T05:27:35Z")
I find Pepto doesn’t work for me - it makes me feel sicker. My MIL also has this problem. She said she only took Pepto twice in her life, and each time she vomited shortly after. When she took something else like Gravol though, she felt better. I wonder if some people have more or different bacteria in the stomach that have an adverse reaction to the active ingredients in the Pepto? ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [October 3, 2005, 12:57pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/4 "2005-10-03T12:57:44Z")
> [@Q.E.D.](#): > > Exact mechanism has not been determined. Wow! who’da thunk it? Great link. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [October 3, 2005, 1:01pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/5 "2005-10-03T13:01:04Z")
Pink Bismuth has been used for treating stomach aliments & the “trots” since the 19th Century, at least. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [October 3, 2005, 1:11pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/6 "2005-10-03T13:11:15Z")
It is probably worth noting that some anti-diarheal meds work by slowing the contractions in the intestines. This allows time for absorbtion. Basically, your sick body is trying to push millions of bacteria out of your system, and doing it so quickly that fluids are not absorbed (explains the bathroom fun). Most anit-diarhea drugs slow the contractions, and allow the fluids to be absorbed. While the sympton is treated, the conseuquence is that your body is not rapidly flushing out millions of bacteria. But most people are happy to avoid the bathroom…if they can get there. ---
**Author:** ![Otanabi](https://avatars.discourse-cdn.com/v4/letter/o/b9e5f3/32.png) [@Otanabi](https://boards.straightdope.com/u/Otanabi)\ **Post date:** [October 3, 2005, 1:36pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/7 "2005-10-03T13:36:32Z")
OK, bismuth subsalicylate does treat diarhea, but did you know that it also neutralizes, ahem, residual bathroom odor? This is purely anectodal. I noticed this side effect quite by accident. Here’s the kicker - this works with an ileostomy. I don’t use it regularly, but if I’m going to be with other people, I do take it so I’m not embarrassed. I’ve long wonderred it people with normal plumbing also notice this. And I’m very curious about how this works. Perhaps it’s the bactericidal action, but that’s just a guess. If that’s so, wouldn’t it also work for people \*with \* colons? ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [October 3, 2005, 2:29pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/8 "2005-10-03T14:29:22Z")
Expanding the inquiry into bismuth … Could you just swallow elemental bismuth and experience the same effects? (Note: I am not going to do this. Just curious.) ---
**Author:** ![BobT](https://avatars.discourse-cdn.com/v4/letter/b/8e8cbc/32.png) [@BobT](https://boards.straightdope.com/u/BobT)\ **Post date:** [October 3, 2005, 4:20pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/9 "2005-10-03T16:20:25Z")
> [@Otanabi](#): > > OK, bismuth subsalicylate does treat diarhea, but did you know that it also neutralizes, ahem, residual bathroom odor? This is purely anectodal. I noticed this side effect quite by accident. > > Here’s the kicker - this works with an ileostomy. I don’t use it regularly, but if I’m going to be with other people, I do take it so I’m not embarrassed. > > I’ve long wonderred it people with normal plumbing also notice this. And I’m very curious about how this works. Perhaps it’s the bactericidal action, but that’s just a guess. If that’s so, wouldn’t it also work for people \*with \* colons? And Immodium worked for my mom that way too. I once told her that I thought I was over the recommended dose and she told me that she had taken twice that amount at times. Of course, she had terminal colon cancer so she wasn’t really too worried about side effects. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [October 3, 2005, 7:00pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/10 "2005-10-03T19:00:42Z")
> [@toadspittle](#): > > Expanding the inquiry into bismuth … > > Could you just swallow elemental bismuth and experience the same effects? (Note: I am not going to do this. Just curious.) The bismuth in pepto is oxidized. I’m also not sure if it’s the whole complex that’s important or not (it may dissociate.) I’d say no. I can’t find an MSDS that has much toxicological info, but I doubt it’s good for you. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [October 3, 2005, 9:23pm UTC](https://boards.straightdope.com/t/how-does-pepto-bismol-work/324506/11 "2005-10-03T21:23:24Z")
Well, strangely enough, PB also tends to settle “queasy” stomach. At least for me. I’ve been under the impression that the reasons were not well understood. I’m fine with that. Ignorance and comfort beat discomfort any day. xo, C.