Raisins and grapes can be toxic to dogs, but they must eat a certain amount per pound of body weight to get sick.
Ingestion of raisins or grapes can cause nausea, vomiting, diarrhea, then increased water consumption, lethargy, and kidney failure in dogs, but the toxicity is dose dependent meaning a big dog would have to eat more than a small dog.
Some dogs are more sensitive than others but a toxic dose is usually 3 grapes/raisins per kilogram of body weight (3 per 2.2 pounds). So one grape is very unlikely to be an issue unless Paris is extremely tiny (less than 2 pounds).
I understand there is a lot of conflicting information out there. To be safe we recommend no grapes or raisins. But they do need to eat a certain minimal amount per pound of body weight.
I always recommend that owners watch their pups for vomiting and/or diarrhea several hours later just in case he ate more then you thought he did. Signs of toxicity usually occur with 12 to 24 hours, but in some cases 48 hours. Further signs of toxicity include lethargy, lack of appetite, abdominal pain, increased water consumption and finally lack of urine production.
I tell owners if they see vomiting and diarrhea with any amount of grapes fed we need to get them on intravenous fluids to protect the kidneys.
Best of luck with Paris, please let me know if you have any further questions.