Side effects of grapes and raisins
Grapes are probably safe when taken orally in medicinal quantities. Eating large amounts of grapes, dried grapes, raisins, may cause diarrhea. Some people have allergic reactions to grapes and grape products. Other potential side effects include upset stomach, indigestion, nausea, vomiting, cough, dry mouth, sore throat, infection, headache and muscle problems.
Special warnings and alerts:
Bleeding: Grapes may slow blood clotting and may increase the chances of bruising and bleeding in people with bleeding conditions. However, there are no reports of it occurring in humans.
Surgery: Grapes may cause blood to clot. This may cause more bleeding during and after surgery. Do not use grapes and their products for at least 2 weeks before surgery.