Frogs can carry parasites and toxins that may be harmful to cats.
Some species of frogs secrete toxins from their skin that can cause serious health issues if ingested.
Suggestions
It is best to avoid allowing your cat to eat frogs.
If your cat catches a frog, monitor for any signs of illness and consult a veterinarian if any symptoms appear.
Note: even if labeled as safe, any food can potentially cause allergies. When introducing a new food, please feed a small amount and observe your cat for any allergic reactions.