A.W.
This is the worst time of year for an outbreak of food poisoning as it's also flu, pluracy, bronchitis, pnemonia, and cold season. It can be very difficult to tell the difference between the flu and food poisoning. A virus such as the flu usually incubates for 72 hours...that's 3 days that you have it and are contagious that you don't even know that you're sick. And a virus can last anywhere from 72 hours to 14 days for your standard strains, although some virus last longer. For the time being, until you take him to the doctor, treat it like the flu. Offer plenty of clear liquids (tea, kool-aid, gatoraide, sprite, 7-up, jello, popsicles, chicken broth)to keep him propperly hydrated. Allow him to eat normally or as much or little as he likes. If he vomits, wait 2 hours before giving him anything...not even water...that way his stomach can settle. Then after 2 hours give him a tablespoon of water and see if he can hold it down. After about 15 or 20 minutes if the water hasn't come back to visit him, then give him an ounce and see if he can hold it down. Then increase it gradually waiting about 15 to 20 minutes between each increase to see if it will come back up. Once you see he can hold the water down, keep him on a clear liquid diet for the next 24 hours, then slowly start introducing solids such as crackers and dry toast. If he gets diarrhea, avoid fruit juice and things high in fiber. A good way to stiffen the bowls is with boiled rice and bananas. Also keep an eye on his temp. Check it every couple of hours. Anything over 101 and you should take him to the hospital to have him checked out. If he suddenly seems to have trouble breathing, you hear a wheeze, he starts turning blue around the mouth or nailbeds, call 911. And watch his color. Some food poisonings will affect the liver. If he starts looking yellow in his skin or the whites of his eyes (jondice)then he needs to go to the hospital. If he's getting severe stomache pains or cramping that keeps him doubled over in pain, take him to the hospital. If he can't even hold water down, take him to the hospital.
Watch for signs of dehydration...can't produce tears, dry mouth, no urine, eyes look sunken in, lips are dry and cracking, etc...that will warrant a trip the hospital also. Or if you're to scared to wait it out until his doctor can see him, then take him to the hospital...they won't get mad at you.