Most cases of gastroenteritis last only a few days, and resolve without treatment. There is no medication that will make it get better any faster, only medications that can control the symptoms. Whenever I talk about viral illnesses, I always mention that antibiotics are completely ineffective against viruses, which is why they are not prescribed for colds, flu, or gastroenteritis.

Another common misconception about gastroenteritis is that when people develop vomiting and diarrhea after eating, they often refer to it as "food poisoning." This is usually not the case. In cases of food poisoning, many people who ate the same food would also be sick, so if only one person gets sick, it's almost always gastroenteritis. There is a connection to food, though: gastroenteritis is spread by what's called the "oral-fecal route:" using the toilet, then not washing hands thoroughly, allowing pathogenic bacteria to spread to everything those hands touch, including food serving equipment. In takes only one sick restaurant employee to sicken hundreds of others. My one hope for something good coming out of the COVID-19 pandemic is that it might be considered foolish to come to work sick. Based on my own observations, I suspect that one reason why people often vomit for the first time immediately after eating is that a full meal stretches the wall of the already-sick stomach, triggering the vomiting.

Treatment of gastroenteritis symptoms: first of all, avoid all solid food while vomiting. There are no medications available without a prescription that control vomiting, so the most effective self-care is called "gut rest:" sticking to a clear liquid diet, so your gastrointestinal tract has as little to do as possible. A clear liquid diet is any liquid you can see through: water, tea without milk, soda, jello, popsicles, broth, etc. Try to consume enough liquids that your urine is no darker than "medium yellow," about the color of apple juice. If you're not having nausea and/or vomiting, you can drink it as fast as you want, but if you're vomiting, just take very small sips, perhaps 1--2 teaspoons at a time, as frequently as you can take it without nausea or vomiting. Lie as still as possible, to avoid any activity that might trigger vomiting. This technique can often make the difference between being able to stay home and having to go to the ER for a bag of IV fluid.

Once you can consume clear liquids without vomiting for 12--24 hours (my best estimate--don't advance too soon), you can advance to a full liquid diet, including pudding, ice cream, soup that has very little solids in it, gravy, etc. Once you tolerate this for 12--24 hours, you can advance to the BRAT diet, adding Bananas, Rice, Applesauce, and Toast. After another 12--24 hours, advance to a regular diet. If symptoms return, restart the clear liquid diet.

The diarrhea with gastroenteritis can cause HUGE volumes of watery stool. It may be hard to believe that your body can produce that much fluid at one time. Fortunately, there are over-the-counter medications available to control diarrhea, with one of two active ingredients: bismuth subsalicylate (kaopectate, Pepto-Bismol, etc.) and loperamide (Imodium). Both work well; I prefer loperamide, because bismuth subsalicylate is usually a chalky liquid; I don't like the texture, and can be messy to transport. Follow the directions on the package.

A common problem with diarrhea is perianal excoriation; irritated skin around your anus. See, the differences between diarrhea and normal stool are that diarrhea contains more water and digestive enzymes. When you have diarrhea, it actually digests the skin around your anus. You can prevent this unpleasant problem by applying a bland ointment (Vaseline, aka petrolatum, A&D ointment, Preparation H, etc.) to the "affected area" after every diarrhea stool. If you are already having pain, you can relieve it by applying toothache get (Oragel) to the area. It contains a local anesthetic; it also contains menthol, so the pain will get worse for a minute or so, then go away. BTW, I have also used this on my doggies when they have diarrhea. If more than one person (or creature) in the household has diarrhea, each should have their own containers of these medications, or steps need to be taken to avoid cross-contamination. If everyone is using the same container, use a clean spoon or other cutlery to remove the correct amount--do not put your fingers into the container.

Symptoms that I would recommend seeking professional help for include:

Orthostatic lightheadedness: "dizziness" or lightheadedness upon standing up. Some people cannot even stand up, because the lightheadedness is so severe. This can be a sign of dehydration. If you cannot stand up for at least two minutes, it's time to get help, which will almost certainly involve bloodwork, IV fluid, and medication.

Hematemesis: bloody vomit. A few flecks of bright red blood in the vomit is not uncommon (and red jello can come back out red), but if the vomit looks like it has coffee grounds in it, go to the ER, and bring a sample of that vomit. "Coffee-ground emesis" is usually a sign of bleeding into the stomach, and may require more aggressive treatment, possibly including the insertion of an NG (nasogastric) tube through the nose and down the throat into the stomach. NG tube insertion is not something anyone would describe as pleasant, but it's usually over with quickly, and you will feel better right away, because they can hook it up to suction, and empty your stomach completely.

Hematochezia: bloody stool. Again, a few flecks of bright red blood are common, but it the stool looks like it has a large amount of red blood, or even a small amount of "tar," go to the ER with a sample of the bloody stool. Again, more aggressive treatment may be required.