If your dog has a mildly upset stomach you may be able to treat it yourself. Feed your dog plain boiled chicken with plain cooked rice in a few small portions a day. Stick to this diet for a few days before getting back to his normal feeding routine by gradually adding small amounts of his usual food into the mix. You could also fast your dog for a day to let his stomach empty from the toxins of the vanilla ice cream. Very importantly, your dog should have access to plenty of fresh, clean water at all times. If you see any serious symptoms including dehydration or lethargy, pain, a hard swollen stomach, blood in vomit or feces, contact a vet immediately.