Definition

What Is Gastroenteritis?

Gastroenteritis is inflammation of the stomach and small intestine, typically caused by infection. Often called "stomach flu" (though unrelated to influenza), it produces a classic syndrome of acute nausea, vomiting, diarrhea and crampy abdominal pain. Most cases are self-limiting and resolve in 1 to 7 days.

Most cases are viral: norovirus (most common adult cause), rotavirus (children), adenovirus¹, sapovirus and astrovirus. Bacterial causes include Salmonella, Campylobacter, E. coli, Shigella, Yersinia and toxin-producing bacteria (food poisoning). Parasitic causes (Giardia, Cryptosporidium) cause more prolonged illness.

The major complication is dehydration, particularly dangerous in young children, the elderly and the immunocompromised³. Most healthy adults manage at home with oral rehydration. Red flag symptoms (bloody diarrhea, high fever, severe dehydration, persistence beyond a week) warrant medical evaluation. Specific treatments exist for certain bacterial and parasitic causes.

💡 Key Insight: Most cases of gastroenteritis are viral and self-limiting. The main treatment is rehydration (oral rehydration solutions or water with electrolytes). Anti-diarrheal medications can prolong illness in bacterial cases. Probiotics may modestly shorten diarrhea, though the evidence is mixed. Antibiotics are not appropriate for most cases.

A torso with an inflamed stomach and intestines, beside icons for nausea, vomiting and diarrhea and a close-up of the viruses or bacteria that cause it

Types of Gastroenteritis

Viral (most cases)

Norovirus (most common adult), rotavirus (children), adenovirus. Self-limiting: usually 1 to 3 days for norovirus, longer for rotavirus. Treatment: rehydration only. Highly contagious, frequent handwashing essential.

Bacterial

Salmonella, Campylobacter, E. coli, Shigella. Often from contaminated food/water. May cause bloody diarrhea, fever. Some require antibiotics; many don't.

Parasitic / Toxin-Mediated

Giardia, Cryptosporidium, prolonged illness. Food poisoning toxins (S. aureus, B. cereus), rapid onset, short duration. Travelers' diarrhea, multiple causes.

Signs & Symptoms

Symptoms of Gastroenteritis

Acute onset of GI symptoms. The pattern of vomiting vs diarrhea and the presence of fever or blood help suggest the cause.

Symptom	What happens
Typical Symptoms
Nausea & Vomiting	Usually first symptom, especially in viral. May be projectile in norovirus. Typically lasts 24 to 48 hours. Vomiting before diarrhea suggests viral; concurrent suggests other causes.
Diarrhea	Frequent watery stools. Viral: large volume, no blood. Bacterial: may be bloody (dysentery). Parasitic: often prolonged. Lasts 3 to 7 days typically.
Abdominal Cramping	Diffuse, crampy. Better after bowel movement temporarily. Severe focal pain suggests other diagnosis (appendicitis, ischemia).
Low-Grade Fever	100.4 to 101.3°F (38 to 38.5°C) typical. Body aches, headache, fatigue common. A high fever, above 102.2°F (39°C), points more toward a bacterial cause or severe disease.
Red Flags (Seek Medical Care)
Severe Dehydration	Dry mouth, no tears, sunken eyes, decreased urination, dizziness when standing. Especially dangerous in children and older adults. IV fluids may be needed. Confusion is an emergency: call 911 or go to the emergency department.
Bloody Diarrhea (Dysentery)	Visible blood or mucus in stools. Suggests invasive bacterial infection (Shigella, EHEC, Campylobacter) or amebiasis. Requires stool studies; sometimes antibiotics.
High Fever Above 102.2°F (39°C)	Suggests bacterial cause, possible bacteremia, more serious disease. Warrants medical evaluation. Stool culture may be indicated.
Persistence >1 Week	Most viral cases resolve within a week. Persistent diarrhea suggests parasitic infection (Giardia), inflammatory bowel disease or another cause. Evaluation warranted.

Causes

Causes of Gastroenteritis

Gastroenteritis is caused by an infection, most often a virus, or by food or drink contaminated with germs or chemicals¹².

Cause	How It Contributes to Gastroenteritis	What Helps
Viruses	Norovirus is the most common cause, with symptoms lasting 1 to 3 days; rotavirus lasts 3 to 8 days and is preventable by vaccine; adenovirus and astrovirus are others¹².	Fluids and oral rehydration solution (Nutritional Strategy), handwashing with soap and water, and rotavirus vaccination for infants (conventional care); antibiotics do not help viral illness
Bacteria	Salmonella, Campylobacter, Shigella and E. coli, mostly from contaminated food or water⁹, more often cause bloody diarrhea, higher fever and a longer illness¹.	Rehydration; a prescribed antibiotic only for selected infections, guided by stool testing, since for some it makes things worse (Treatment Comparison; conventional care)
Parasites	Giardia, Cryptosporidium and Entamoeba cause a smaller share, often with a longer illness⁹.	Stool testing and a prescribed antiparasitic medicine (conventional care)
Contaminated food or drink	Food poisoning is gastroenteritis from food or drink contaminated with viruses, bacteria, parasites or chemicals¹².	Rehydration (Nutritional Strategy) and safe food preparation and storage
Spread between people	Germs pass through traces of stool or vomit on hands, surfaces and food; norovirus can be shed for up to 2 weeks after recovery and survive for months on surfaces¹². Unsafe water and poor sanitation drive most cases worldwide⁹.	Handwashing with soap and water, cleaning surfaces and staying home from work or school until 2 days after the last episode¹³

Treatment Comparison

Conventional and Holistic Treatment for Gastroenteritis

🌿 HOLISTIC

💊 CONVENTIONAL

🌿

Holistic / Functional Approach

Rehydration and supportive nutrition are first-line for most uncomplicated cases; probiotics are optional and their benefit is uncertain⁵.

Hydration Priority

Oral rehydration solution (ORS), sodium + glucose ratio crucial. Commercial packets or ready-made solutions.

Probiotics

May shorten acute infectious diarrhea by about a day, though two large trials in children found no benefit. S. boulardii and certain Lactobacillus strains are the most studied.⁵

Microbiome Recovery

Fermented foods and fiber are reasonable once eating normally; evidence that they speed recovery of gut bacteria is limited

Hand Hygiene

Critical: norovirus is highly contagious. Soap and water (alcohol gel ineffective for norovirus).

Full Holistic Approach Includes

Aggressive oral rehydration: sip frequently rather than large volumes. Commercial ORS preferred over plain water or sports drinks (wrong electrolyte ratios). Coconut water is low in sodium, so it does not replace ORS.
If vomiting, take small sips (1 to 2 tablespoons, 15 to 30 mL) every few minutes, and drink more once the vomiting settles. Try ice chips if larger amounts trigger vomiting.
Probiotics: Saccharomyces boulardii 250 mg (about 5 billion CFU) twice a day may shorten illness by about a day; the two large trials in children that found no benefit tested Lactobacillus products, which are not recommended here. Use caution with a weakened immune system or a central line, as bloodstream infections from probiotics have been reported; agree on it with your team.
Return to normal food as soon as you can tolerate it. The traditional BRAT diet (bananas, rice, applesauce, toast) is no longer recommended, because it is nutritionally inadequate and delays recovery. Bananas, rice and applesauce are fine if they appeal, but need not be all you eat.⁴
Bone broth: provides electrolytes, amino acids and hydration; easily tolerated
Ginger tea may help nausea. Sip slowly.
Avoid until tolerated: dairy, fatty foods, very spicy foods, alcohol, caffeine
Disinfect surfaces with bleach-based cleaners for norovirus. Wash bedding/clothes in hot water.
Isolate sick household members, separate bathroom if possible; no shared utensils
Rest: stay home from work/school until 48 hours symptom-free.
Gradual diet advancement: rehydration first, then normal food as tolerated, usually within a day or two
Avoid anti-diarrheals (loperamide) if bloody diarrhea⁶; they can worsen invasive bacterial infections by retaining toxins
After the illness: fermented foods (kefir, sauerkraut, kimchi) and fiber are fine as tolerated

✅ Most Cases Self-Resolve: Virtually all viral gastroenteritis resolves in 1 to 7 days with adequate hydration. Antibiotics are not helpful for viral cases and may worsen some bacterial cases. Seek medical care for red flag symptoms, for dehydration and for any illness in a baby under 12 months.

💊

Conventional / Medical Approach

Rehydration (IV if severe) + targeted antibiotics for specific bacterial/parasitic causes only

Most Cases

Supportive, oral rehydration; symptom management; observation

Severe Dehydration

IV rehydration in ER or hospital. Electrolyte correction. Kidney function monitoring.

Bacterial (Selected)

Antibiotics for severe Shigella, Salmonella in immunocompromised, Campylobacter with severe symptoms

Parasitic

Metronidazole/tinidazole (Giardia); nitazoxanide (Cryptosporidium); diloxanide (amebiasis)

Conventional Approach Includes

Oral rehydration solution (ORS): first-line for mild to moderate dehydration.
IV rehydration: for severe dehydration, intractable vomiting, hypotension. Normal saline or lactated Ringer's. Potassium replacement if low.
Anti-emetics (ondansetron): 4 to 8 mg as a dissolving tablet in adults, reduces vomiting and helps keep fluids down. Also used in children, at a weight-based dose set by a clinician.
Anti-diarrheals (loperamide): for non-bloody diarrhea only. Avoid with fever, blood, severe illness, C. difficile suspicion, and in young children.
Bismuth subsalicylate: useful for travelers' diarrhea, mild gastroenteritis. Avoid in children (Reye syndrome risk).
Selective antibiotics: most cases do not need antibiotics. Indications: severe Shigella, prolonged Salmonella in high-risk, severe Campylobacter, travelers' diarrhea with severe symptoms, specific identified bacteria with clinical indication.
Not for EHEC (E. coli O157:H7): antibiotics increase risk of hemolytic uremic syndrome
Not for routine Salmonella: antibiotics prolong carriage
Azithromycin or ciprofloxacin: empiric for severe travelers' diarrhea
Metronidazole: for Giardia or amebiasis, at the dose and length your clinician sets for the infection found; no alcohol during the course and for at least 3 days after
Nitazoxanide: Cryptosporidium, alternative for Giardia
Hospitalization: for severe dehydration, inability to keep down fluids, electrolyte abnormalities, immunocompromised with severe disease

⚠️ Avoid Inappropriate Antibiotics: For some bacterial causes (EHEC, Salmonella), antibiotics increase complications or prolong carriage. Stool testing should guide antibiotic decisions, not "just in case" prescribing.

Nutritional Strategy

Diet for Gastroenteritis

Rehydrate first, keep rehydrating, then return to normal food as soon as it is tolerated, usually within a day or two.

What to drink and eat during gastroenteritis, and what to avoid

What to eat or do	Details
✅ Prioritize:
ORS (Oral Rehydration Solution)	Commercial ORS, or homemade (about 4 cups, 1 L, of water + 6 tsp sugar + 1/2 tsp salt). Correct electrolyte balance. Better than sports drinks.²
Eating again after the worst passes	Bananas, rice and applesauce are fine if they appeal, alongside a normal diet as soon as it is tolerated; there is no need to restrict yourself to them.
Bone Broth & Soups	Electrolyte-rich, hydrating, easily tolerated. Chicken broth, miso soup. Sip slowly as the nausea improves.
Plain Yogurt / Kefir (As Recovering)	Contains live cultures; fine once tolerated. Avoid initially if vomiting/severe diarrhea; introduce as recovering.
Ginger (For Nausea)	Ginger tea, fresh ginger in broth. It may help nausea, with the best evidence in pregnancy¹⁴. Sip slowly.
❌ Avoid Until Recovered:
Dairy (Initial Phase)	Temporary lactose intolerance common after viral gastroenteritis. Avoid milk and cheese for the first few days. Yogurt and kefir are fine as you recover.
Fatty / Fried / Greasy Foods	Hard to digest, may worsen diarrhea. Reintroduce gradually as symptoms improve.
Very Spicy Foods	Irritate inflamed gut. Reintroduce gradually after recovery.
Caffeine, Alcohol	Diuretic effect worsens dehydration. Avoid during illness and 24 to 48 hours after.
Sugary Drinks / Sodas	High sugar can worsen diarrhea (osmotic load). Wrong electrolyte composition. Use ORS instead.

Supplement Protocol

Evidence-Based Supplements for Gastroenteritis

Zinc in children, and possibly probiotics, can shorten duration. Most important: hydration.

Supplement	What it is for	Typical range	Timing	Notes & cautions
Saccharomyces boulardii	Yeast probiotic. May shorten diarrhea by about a day; the two large trials in children that found no benefit tested Lactobacillus products, not this yeast. Resistant to antibiotics.	250 to 500 mg (about 5 to 10 billion CFU) twice a day	With or without food	Use throughout illness and 1 to 2 weeks after. Use caution with a weakened immune system or a central line, as bloodstream infections from probiotics have been reported; agree on it with your team.
Lactobacillus rhamnosus GG	Best-studied bacterial probiotic for acute gastroenteritis, but a trial in 971 young children found it did not shorten diarrhea or reduce severity⁵.	Not recommended for gastroenteritis (the trial used 10 billion CFU twice a day)	Not applicable	Rehydration comes first.
Zinc (Children)	WHO recommends it for diarrhea in children: it shortens the illness and reduces stool volume⁹.	20 mg/day for children >6 months; 10 mg for <6 months	With food, 10 to 14 days	Especially important in resource-limited settings. This WHO treatment dose is above the usual upper intake level for young children and is for a course of 10 to 14 days only, on your pediatrician's advice.
Bismuth Subsalicylate	Mild antimicrobial + anti-inflammatory. Effective for mild travelers' diarrhea.	262 to 525 mg every 30 to 60 min, up to 8 doses/day	Between meals	Avoid in children and teenagers (Reye syndrome). It contains a salicylate: do not take it if you are allergic to aspirin or have an ulcer or a bleeding problem, and ask first if you take a blood thinner or medicine for diabetes, gout or arthritis¹⁵. Causes black tongue/stool, harmless.
Activated Charcoal	Binds some substances in the gut; not a standard treatment for gastroenteritis, with little evidence of benefit.	1 to 2 g every 4 to 6 hours	Away from medications (2 hours)	Use briefly. Don't combine with medications; it will adsorb them.
Ginger	Studied for several kinds of nausea; it may help nausea in pregnancy, and evidence for other nausea is less certain¹⁴.	1 to 2 g/day as tea, capsules or fresh	Throughout day	Can cause abdominal discomfort, heartburn or diarrhea. If you take any medicine, check with your healthcare provider first¹⁴.
L-Glutamine	Proposed to support the gut lining; human evidence in post-infectious recovery is limited.	5 to 15 g/day	Between meals	Not established: one trial of 106 adults found benefit in people developing post-infectious IBS¹⁶, still to be confirmed in larger trials.
Vitamin D3	Not a gastroenteritis treatment; continue any usual supplement.	Set the dose with your clinician; most adults need no blood test first	With a fat-containing meal	Continue baseline supplementation.

What to Expect

What to Expect Over Time

Most gastroenteritis settles on its own within days; rehydration is the treatment, and the bacterial or parasitic infections that need medicine are treated with a prescription.

Treatment and supportive care, together

First Weeks

Sip fluids often; oral rehydration solution replaces lost water and salts⁹. Vomiting usually stops in 1 or 2 days and diarrhea within 5 to 7 days¹³. Eat normally as soon as you can⁴. Dairy may be hard to tolerate for a few days. Infections that need treatment are treated with prescribed medicine chosen on stool testing.

Months 1 to 3

Most people have recovered. Diarrhea lasting beyond 7 days needs a doctor¹³.

Months 3 to 12

Some people have bowel symptoms that last for months, more often after bacterial or parasitic infection¹¹; see a doctor rather than self-treating.

Long Term

Handwashing, safe water and food hygiene, and rotavirus vaccination for infants help prevent further episodes⁹.

When to Seek Care

Call 911 or go to the emergency department, without waiting or trying diet first, for vomiting blood or green vomit, sudden severe abdominal pain, a stiff neck or sudden severe headache, blue, gray or blotchy skin, severe breathing difficulty or confusion¹³. Get a same-day appointment for dehydration, especially in babies, young children and older adults: few or no wet diapers, no tears, sunken eyes, dark urine or dizziness. Also for fluids not staying down, bloody diarrhea, high fever or any illness in a baby under 12 months¹²¹³.

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References & Evidence Notes

Each numbered entry below is either a source you can follow or a note setting out what the evidence does and does not support. Both are numbered together so the markers in the text line up.

Last reviewed October 20, 2026. Supplement entries are cross-checked against the NIH National Center for Complementary and Integrative Health and the Linus Pauling Institute Micronutrient Information Center.⁷ Most gastroenteritis in a healthy adult settles on its own, and the whole job is replacing fluid and salts faster than you lose them. The danger is dehydration, and it arrives fastest in babies, small children, older adults, and anyone immunosuppressed or pregnant. Get a same-day appointment for blood in the stool, a high fever, localized abdominal pain, vomiting that prevents any fluid staying down, signs of dehydration such as no urine for eight hours or sunken eyes, or illness lasting beyond a week. Call 911 or go to the ER for drowsiness or confusion, or for sudden severe abdominal pain. In an infant, dehydration can become serious within hours, so the threshold for being seen should be very low. Do not take an anti-diarrheal if there is blood in the stool or a high fever, because slowing the gut can make certain bacterial infections worse.

On causes and course: viral gastroenteritis, most commonly norovirus in adults and rotavirus in unvaccinated children, accounts for the large majority of cases and is usually self-limiting within one to three days. Bacterial causes including Salmonella, Campylobacter, Shigella and Shiga toxin-producing E. coli are a smaller share and are more often associated with bloody diarrhea, higher fever and a longer illness. ↩
On oral rehydration, which is the treatment: oral rehydration solution works because glucose and sodium are absorbed together by the same intestinal transporter, which pulls water across with them, and this pathway keeps working during infection; that cotransport rationale is the basis of the formulation, PubMed 31813065. That is why the ratio matters and why sports drinks, which are high in sugar and low in sodium, are a poor substitute and can worsen osmotic diarrhea. Commercial ORS packets are inexpensive and correctly formulated; WHO publishes the composition. ↩
On who is at risk: infants and young children dehydrate faster because of a higher surface area to volume ratio and higher baseline fluid turnover, and older adults are at risk through blunted thirst, diuretics and reduced renal concentrating ability. In both groups the threshold for medical review should be low. Pregnancy, immunosuppression, inflammatory bowel disease and recent antibiotic use also change the picture, the last raising the possibility of C. difficile. ↩
On the BRAT diet, which is no longer recommended: bananas, rice, applesauce and toast were standard advice for decades. Pediatric guidance moved away from it because it is low in protein, fat and energy, and because prolonged restriction delays recovery of the intestinal lining. Current advice is early return to a normal, age-appropriate diet once rehydration is under way, typically within a day. Those foods are perfectly fine to eat; restricting yourself to them is the part that was wrong. ↩
On probiotics: Saccharomyces boulardii and certain Lactobacillus strains have randomized evidence for modestly shortening the duration of acute infectious diarrhea, on the order of a day. Two large trials in children presenting to emergency departments found no benefit: one of Lactobacillus rhamnosus GG in 971 children in the US found no difference in how long diarrhea lasted, PubMed 30462938, and one of a two-strain Lactobacillus product in 886 children in Canada found no reduction in moderate to severe illness, PubMed 30462939, so the effect is neither large nor certain. Low risk, modest and uncertain benefit, and no substitute for rehydration. ↩
On antimotility agents: loperamide can reduce symptoms in uncomplicated watery diarrhea in adults, but is avoided where there is bloody diarrhea, high fever, or suspected C. difficile or Shiga toxin-producing E. coli, an avoidance surveillance data show is imperfectly followed in practice, PubMed 21467017, because slowing transit retains toxin and has been associated with more severe disease including hemolytic uremic syndrome. It is not used in young children. ↩
National Center for Complementary and Integrative Health (NIH), nccih.nih.gov, and the Linus Pauling Institute Micronutrient Information Center, lpi.oregonstate.edu/mic. ↩
On how common acute diarrheal illness is: four 12-⁠month population surveys in the US, with 52,840 interviews, found a monthly prevalence of 5.1%, corresponding to 0.6 episodes per person per year, with rates highest in children under 5, PubMed 17291364. ↩
On diarrheal disease worldwide: the World Health Organization reports nearly 1.7 billion cases of childhood diarrheal disease a year and about 443,832 deaths a year in children under 5, making it the third leading cause of death in children aged 1 to 59 months; it names contaminated food and water as the main sources and recommends oral rehydration solution, zinc for children, safe water, sanitation, handwashing and rotavirus vaccination, WHO. ↩
On norovirus: CDC estimates 19 to 21 million norovirus illnesses in the US each year, with about 109,000 hospitalizations and 900 deaths, mostly among adults aged 65 and older, CDC. ↩
On lasting symptoms: a meta-analysis of 45 studies with 21,421 people found that 10.1% met criteria for irritable bowel syndrome 12 months after infectious gastroenteritis, rising to 41.9% after protozoal or parasitic and 13.8% after bacterial infection, PubMed 28069350. ↩
On causes, spread and when to see a doctor: the National Institute of Diabetes and Digestive and Kidney Diseases names norovirus as the most common cause of viral gastroenteritis, describes spread through stool and vomit, and advises seeing a doctor right away for signs of dehydration, with a lower threshold for infants, older adults and people with weakened immunity, NIDDK. ↩
On how long it lasts and emergency signs: the NHS says diarrhea usually stops within 5 to 7 days and vomiting within 1 or 2, advises staying off work or school until 2 days after symptoms stop, and lists the signs that need emergency care, NHS. ↩
On ginger: the National Center for Complementary and Integrative Health notes that ginger has been studied for several types of nausea and vomiting, that research shows it may help nausea and vomiting in pregnancy, that it is uncertain whether it helps nausea from chemotherapy or after surgery, that it can cause abdominal discomfort, heartburn, diarrhea and mouth and throat irritation, and that anyone taking a medicine should talk with a healthcare provider before using it, NCCIH, ginger. ↩
On bismuth subsalicylate: the US over-the-counter label warns that it contains salicylate, that it should not be taken by anyone allergic to salicylates including aspirin, or with an ulcer or a bleeding problem, that children and teenagers who have or are recovering from chickenpox or flu-like symptoms should not use it because of Reye syndrome, that people taking medicine for anticoagulation, diabetes, gout or arthritis should ask a doctor or pharmacist first, and that darkening of the stool or tongue is temporary and harmless, DailyMed, bismuth subsalicylate labels. ↩
On glutamine after infection: a randomized trial in 106 adults who developed irritable bowel syndrome with diarrhea and increased gut permeability after an enteric infection found that glutamine 5 g three times a day for 8 weeks reduced symptom scores more than placebo, and the authors called for large trials to confirm it, PubMed 30108163. ↩

Test	What it shows
Clinical & Initial Evaluation
Clinical Diagnosis	Most cases diagnosed clinically. Acute onset diarrhea ± vomiting, mild fever, exposure history. Testing reserved for severe, prolonged, immunocompromised or red-flag cases.
Exposure History	Recent travel (travelers' diarrhea), food exposures (potlucks, restaurants), sick contacts, antibiotic use (C. difficile), childcare/school exposure (viral).
Hydration Assessment	Vital signs (blood pressure lying and standing), skin elasticity, mucous membranes, urine output, weight loss. Most important clinical assessment.
Abdominal Examination	Rules out surgical conditions, appendicitis (tenderness low on the right of the abdomen), ischemia, obstruction. Diffuse mild tenderness expected in gastroenteritis.
Laboratory (Selected Cases)
Stool Studies	For bloody diarrhea, severe illness, immunocompromised, prolonged symptoms. GI PCR panel detects multiple pathogens. Stool culture, ova and parasites, C. difficile toxin.
Basic Metabolic Panel (Electrolytes)	For severe symptoms, assess hydration, kidney function, electrolyte abnormalities (hypokalemia from vomiting, acidosis from severe diarrhea).
CBC, Inflammatory Markers	For severe disease, suspected bacterial cause. Leukocytosis common. Anemia raises concern for chronic disease or significant blood loss.
C. difficile Testing	If recent antibiotics or hospitalization, healthcare exposure. Stool toxin or PCR. See dedicated C. difficile page.

Gastroenteritis

What Is Gastroenteritis?

Types of Gastroenteritis

Viral (most cases)

Bacterial

Parasitic / Toxin-Mediated