Mary, 4-6 ounces of milk chocolate will not be life-threatening to Ollie; she may vomit or get diarrhea otherwise she will be fine. I would keep an eye on her for the next 24 hours, if she vomits or gets diarrhea this is what you can do:
1- Do not give things like Pepto Bismol or Imodium. Start her on Pepcid AC (famotidine) 10mg tablet every 12 hours for 1-2 days. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 8-12 hours. Need to give her gastrointestinal tract time to rest.
3- After 8-12 hours offer a small amount of water. Wait half hour, if no vomiting, offer a small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day. Keep on this diet for several days then wean into regular diet.
4- If she continues to vomit after doing the above she will need to be seen by your family veterinarian for a hands on examination. Symptoms that would require an ER vet visit are abdominal swelling, pale gums, hyperactivity, muscle tremors, etc.
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