Sharting happens when liquid or soft stool slips out alongside gas you intended to pass. It’s essentially a misfire in the system your body uses to tell the difference between gas and stool. While embarrassing, it’s surprisingly common: roughly 1 in 12 adults worldwide experience some form of accidental bowel leakage, with rates higher in women and people over 60.
Understanding why it happens starts with how your body normally keeps things sorted, and what can throw that system off.
How Your Body Tells Gas From Stool
Your rectum and anal canal run a constant screening process that most people never think about. When material moves into the lower rectum, a reflex called the rectoanal inhibitory reflex briefly relaxes part of your internal anal sphincter, the involuntary muscle that stays clenched by default. This partial relaxation lets a small amount of rectal contents reach the upper anal canal, where specialized nerve endings “sample” what’s there. Your brain then decides: safe to release gas, or time to find a bathroom.
Two muscles work together to execute that decision. The internal anal sphincter operates automatically, keeping things sealed without you thinking about it. The external anal sphincter is the one you control voluntarily, the squeeze you use when you’re holding it in. When everything works properly, you can relax just enough to pass gas while the external sphincter holds back anything solid or liquid.
A shart happens when this sampling system gets fooled. If stool is unusually loose or watery, it can slip past during a moment of relaxation meant only for gas. The nerve endings in the anal canal have a harder time distinguishing between air and liquid than between air and solid stool, which is why sharting almost always involves soft or watery stool rather than formed stool.
Loose Stool Is the Biggest Risk Factor
The single most important variable is stool consistency. On the Bristol Stool Chart, a clinical tool that classifies stool into seven types, anything rated type 5 through 7 (soft blobs, mushy pieces, or fully liquid) is more likely to leak during gas. These softer forms move through the colon faster and are harder for the sphincter muscles to hold back during the brief relaxation that accompanies flatulence.
Anything that makes your stool looser increases your chances of a shart. That includes obvious triggers like a stomach bug, but also subtler everyday factors like diet, caffeine intake, and food intolerances.
Dietary Triggers That Loosen Stool
Caffeine is one of the most common culprits. It stimulates contractions in the colon, speeding up transit time and pulling more water into the intestines. Population data shows that for each unit increase in caffeine intake, the risk of chronic diarrhea rises by about 4%. Coffee, tea, and energy drinks all contribute. If you’ve noticed sharting tends to happen after your morning coffee, this is likely why.
Sugar alcohols like sorbitol and xylitol, found in sugar-free gum, diet candies, and some protein bars, are poorly absorbed in the small intestine. They draw water into the bowel through osmosis, producing loose, gassy stool. It’s a combination practically designed to cause a shart: excess gas paired with liquid stool.
Greasy or high-fat meals can also speed up gut motility and soften stool, especially if you eat a large portion quickly. Spicy foods irritate the intestinal lining in some people, producing a similar effect. Alcohol, particularly in large amounts, disrupts fluid absorption in the gut and frequently causes next-day loose stools.
Food Intolerances and the Osmotic Effect
Lactose intolerance is a textbook example of how food intolerances lead to sharting. When your body lacks enough of the enzyme that breaks down lactose (the sugar in milk and dairy), the undigested lactose passes into the large intestine intact. There, it pulls water into the bowel to balance out the concentration of dissolved sugars, a process called osmotic secretion. At the same time, gut bacteria ferment the lactose, producing hydrogen gas and short-chain fatty acids. The result is a combination of bloating, excessive gas, and watery stool, all at once.
Fructose malabsorption works the same way and is triggered by fruit juices, honey, and high-fructose corn syrup. Gluten sensitivity and celiac disease can also produce chronic loose stools and excess gas. If sharting happens repeatedly after specific foods, an undiagnosed intolerance is worth considering.
Stomach Bugs and Acute Illness
Viral gastroenteritis, commonly called the stomach flu, is one of the most frequent causes of sudden, unexpected sharting. These infections inflame the intestinal lining and produce watery diarrhea, abdominal cramping, and nausea. During an active infection, stool can be almost entirely liquid, making it nearly impossible for the sampling reflex to correctly distinguish gas from stool. The sheer volume and speed of intestinal contents overwhelm the sphincter’s ability to hold back.
Bacterial infections from contaminated food produce similar effects. Even after the worst symptoms resolve, the gut can remain irritable for days or weeks, leaving you vulnerable to leakage during that recovery window.
IBS and Chronic Bowel Conditions
People with irritable bowel syndrome, particularly the diarrhea-predominant subtype (IBS-D), face a significantly higher risk. Research comparing IBS patients in the U.S. and Sweden found that fecal incontinence was strongly linked to having more than four bowel movements per day, frequent loose or watery stools, and a sense of urgency. About 23% of IBS patients in both study groups had the diarrhea-predominant form.
Interestingly, the study found no difference in rectal sensitivity between patients who experienced leakage and those who didn’t. The problem isn’t that the rectum is more sensitive; it’s that the stool is too loose and moves too quickly for the normal control mechanisms to keep up. Inflammatory bowel diseases like Crohn’s and ulcerative colitis create similar conditions through chronic intestinal inflammation.
Pelvic Floor and Muscle Weakness
Sometimes the issue isn’t what’s happening inside the intestines but the strength of the muscles holding everything in. The pelvic floor is a hammock of muscles supporting the bladder, rectum, and (in women) the uterus. When these muscles weaken, the external anal sphincter loses some of its ability to clamp down during moments of gas release.
Common causes of pelvic floor weakening include vaginal childbirth, aging, chronic straining from constipation, obesity, and nerve damage from conditions like diabetes or spinal injuries. Rectal prolapse, where the rectum drops down toward or through the anus, also compromises the seal. Kegel exercises, which involve repeatedly tightening and releasing the pelvic floor muscles, can improve sphincter strength and reduce episodes of leakage over time.
Why It Happens More as You Age
The global prevalence of accidental bowel leakage is about 4.9% in adults under 60 but jumps to 9.3% in those 60 and older. Several factors converge with age. The internal anal sphincter gradually loses muscle tone, reducing its baseline resting pressure. Nerve signaling between the rectum and brain slows, making the sampling reflex less reliable. Pelvic floor muscles weaken from decades of use. And older adults are more likely to take medications, like certain antibiotics, blood pressure drugs, or metformin, that soften stool as a side effect.
Reducing Your Risk
The most practical step is keeping your stool on the firmer side of normal. Soluble fiber from sources like oats, psyllium husk, and bananas absorbs excess water in the intestines and adds bulk. Cutting back on caffeine, sugar alcohols, and any food you suspect triggers loose stools makes a noticeable difference for most people. If dairy consistently causes gas and soft stool, try eliminating it for two weeks to see if the pattern changes.
Pelvic floor exercises help regardless of age or sex. The basic technique involves squeezing the muscles you’d use to stop urinating midstream, holding for a few seconds, then releasing. Done consistently, these exercises strengthen the external sphincter and give you better control during gas release. When you feel the urge to pass gas and aren’t sure what’s behind it, especially during illness or after a rich meal, finding a bathroom first is the simplest form of prevention.