I usually keep a supply of stuff I would need when I'm sick, so I won't have to go to the store. If you're going to get sick, you won't get a lot of warning, so it's better to have it ready. I keep handy: Ibuprofen, Sudafed antihistamine, Kleenex, Gatorade, Immodium, Pepto Bismol, the Walmart version of Tums (it tastes better). I also keep a dollar store wastebasket handy for vomiting.
I learned something that seems valuable to me from a veterinarian I worked for. People tend to mix colds and allergy attacks, when they are two entirely separate things. The vet said, if you don't have an elevated temperature, you're having an allergy attack, not a cold. If you don't deal with it immediately, it will turn into a sinus infection. Now, as soon as I develop a headache and a runny nose, I run for the Ibuprofen and Sudafed (generic). If I delay dealing with it, it gets out of hand, and I get sick.
There isn't much you can do with the intestinal flu or food poisoning. If you've got something nasty inside, you have to let it escape. Don't bother taking oral meds until the vomiting is mostly stopped, because it won't stay down. Don't take the Immodium until the worst of the diarrhea is over, because you don't want to retain nasty stuff inside. Take the recommended dosages, don't over-do it; more is not better.
