We’re just going to say it – diarrhea is not pleasant. When it strikes, most people aren’t asking why; they just want relief. Fast. That pink liquid might be the icon of relief, but it doesn’t do the trick every time.
Loose stools can happen for a variety of reasons, and the aisle full of anti-diarrheal options targets different causes. Before you knock back a capful of bismuth (the pink stuff we know so well), it’s worth understanding what might really be going on.
Same Word, Different Experience
We tend to use the word diarrhea to describe loose stools, but clinically, it’s more nuanced. It can be defined by frequency, consistency, urgency, or even incontinence. On top of that, doctors categorize it as either acute (sudden onset) or chronic (lasting weeks or more). Those distinctions matter when it comes to treatment.
Although not exhaustive, it is helpful to know some reasons for extended potty breaks. The common thread is diarrhea, but there are other symptoms to help you differentiate them.
Functional Disorders
Functional disorders like IBS (irritable bowel syndrome) are chronic and often come with symptoms such as bloating, abdominal cramping, urgency, and alternating constipation and diarrhea. Anti-diarrheals, such as loperamide, may provide symptom relief during flare-ups; however, tracking symptoms and identifying trigger foods or stressors are key to long-term management. Because IBS is multifactorial, OTCs should be considered supportive, rather than standalone, tools.
Pathogens
Intestinal pathogens such as norovirus, E. coli and Giardia can not only cause diarrhea, but also lead to nausea, vomiting, fever, fatigue, and abdominal pain. Immediate hydration is crucial, and in some cases, medical treatment may be necessary. While OTC options like bismuth subsalicylate or loperamide may ease symptoms, they should be used with caution and typically avoided if there’s fever, blood in the stool, or suspected bacterial infection, as they can prolong or worsen illness.
Medications / Drugs
Medications, including antibiotics, magnesium-containing products, or chemotherapy, can disrupt normal intestinal flow by altering gut bacteria, irritating the GI lining, or increasing fluid secretion into the bowel. If symptoms persist, consult your doctor about adjusting the dosage or switching to a different medication. Depending on the cause, some over-the-counter (OTC) anti-diarrheals may offer temporary relief. However, in cases involving certain antibiotics or infections, especially when toxins or harmful bacteria are present, slowing gut movement can do more harm than good. By inhibiting motility, these medications may trap pathogens or toxins in the intestines for a longer period, potentially worsening inflammation or prolonging the illness.
Food Allergies & Sensitivities
Food sensitivities such as lactose or gluten intolerance and fructose malabsorption can cause discomfort, bloating, gas, and loose stools, especially after eating trigger foods. Reading ingredient labels and using enzyme supplements when needed can help prevent symptoms. Anti-diarrheals may temporarily mask symptoms, but clearing the irritant from your system and avoiding repeat exposure is more effective and safer than relying on short-term fixes.
Motility
Gut motility and secretion disruptions from stress and anxiety can be just as uncomfortable as anything else listed here. Plus, chronic stress can cause a whole host of other mental and physical discomforts. Engaging in mind-body techniques such as breathwork, behavioral therapy, or gentle exercise can help alleviate stress and reduce gut symptoms over time. OTC anti-diarrheals may help in a pinch, but addressing the stress itself is more sustainable than constantly reaching for short-term symptom control.
Inflammation
Inflammatory conditions such as Crohn’s disease or ulcerative colitis are accompanied by symptoms like persistent diarrhea, blood or mucus in the stool, abdominal pain, fatigue, and unintended weight loss. These conditions require medical management, and early diagnosis and treatment can help prevent long-term damage. OTC anti-diarrheals may help manage urgency or frequency in some cases, but they do not treat the underlying inflammation and should only be used under medical supervision.
Traveling
Traveler’s diarrhea from contaminated food or water acts the same as intestinal infections… because that’s typically what it is. Sometimes it requires medical attention, and other times it subsides with proper at-home care. Preventive measures, such as drinking bottled water, practicing hand hygiene, and avoiding raw or unpasteurized foods, can help lower your risk while abroad. OTCs such as bismuth subsalicylate or loperamide can ease symptoms, particularly for mild cases or when travel plans require quick relief, but they aren’t a cure, especially if infection is involved.
Match the Med to the Move
Over-the-counter (OTC) options for diarrhea aren’t all the same, and some of the conditions listed require more than a trip to the drugstore. If you’re experiencing severe abdominal pain, dehydration, fever, or signs of blood in your stool, then it’s time for urgent care, either at a walk-in or an ASAP visit to your primary care physician. OTCs are for the management of mild symptoms, and even the packaging will advise you to see the doctor if your bowel woes last more than a few days.
Here’s a quick breakdown of common ingredients in drugstore selections, as well as some preventatives, and what they’re good for:
Bismuth subsalicylate is the active ingredient in products like Kaopectate or Pepto-Bismol. (Note: Kaopectate active ingredients have changed over the years and may be different overseas. In the U.S., the active ingredient is bismuth subsalicylate.) It works by coating and protecting the stomach lining, reducing inflammation, and decreasing the flow of fluids into the intestines, which helps to make stools less watery.
It was thought to have prophylactic antimicrobial properties that could help with situations like Traveler’s diarrhea, but recent research1 may suggest otherwise. Heartburn, upset stomach, indigestion, burping, stomach fullness, or gas might be where this one is more useful.
Loperamide hydrochloride, the main ingredient found in Immodium or Immodium A-D. It reduces peristalsis (the wave-like gut contractions that move things along) by binding to specific receptors in the intestinal wall. Because it reduces motility (movement), the intestines have extra time to absorb water, which can help prevent dehydration and ease the frequency of bowel movements. This one is best suited for sudden, non-infectious diarrhea that can be instigated by stress, certain foods, or IBS flare-ups.
Digestive enzymes, found in products like Lactaid, help the body break down specific components of food, such as lactose, fats, or proteins, that some people can’t digest efficiently on their own. In the case of lactose intolerance, for example, supplemental lactase breaks down milk sugar before it reaches the colon, where it would otherwise ferment and cause gas, bloating, or diarrhea. These enzymes don’t treat diarrhea directly, but they can prevent it when symptoms are tied to food intolerances. They’re best used before eating offending foods to reduce the risk of digestive upset.
Fiber supplements, including psyllium husk or methylcellulose, absorb excess water and add bulk to stools, meaning they’re less loose and more formed. However, they aren’t fast-acting and can take a few days to notice a difference. This is more of a preventative measure, making it better for managing mild or chronic diarrhea over time rather than treating acute episodes.
Probiotics are not fast-acting, but can help restore the natural balance of gut bacteria, especially after disruptions like antibiotic use or gastrointestinal infections. Products with high colony counts and enteric coating (which protects the bacteria from stomach acid so they reach the intestines) are typically more effective. While they won’t stop diarrhea quickly, they can support long-term gut health and help rebuild a more resilient microbiome.
Know When to Stop Guessing
Taping a faucet leak only works for so long, so if your bowel troubles are persistent and you aren’t sure why, see a healthcare professional. As with anything you consume, be sure to take into consideration any other medications you are taking to prevent adverse drug interactions. Even other OTCs, vitamins, supplements, or herbal remedies can be a bad combo. If you are unsure, contact your prescribing physician or pharmacist.
If you are experiencing unusual bowel habits after any kind of surgery, check in with your care team to rule out complications and ensure proper recovery.
- Angelo, K. M., Salah, Z., Rogova, M., Plumb, I. D., Walker, A. T., Prentice-Mott, G., Waraich, C., Kim, S., Ryan, E., LaRocque, R. C., Oliver, E., Heitzinger, K., Perry-Dow, K. A., & Connor, B. A. (2025). Efficacy of Bismuth Subsalicylate on the Prevention of Travellers’ Diarrhoea, 2018-2023. Journal of Travel Medicine. https://doi.org/10.1093/jtm/taaf047.
