1.You can end up putting on weight.
2. They might lead to constipation and stomach problems.
3. Grapes might create problems during pregnancy and lactation.
4. Too many grapes aren't good for your kidney.
5. They might lead to allergic reactions.
6. They can lead to acute acidity.
7. They might give you gut problems.
8. They will overload your body with fibres.
Grapes in moderate quantities are beneficial to the body.
But anything beyond the normal quantity isn't good.