Periwinkle is also used for treating diarrhea, vaginal discharge, throat ailments, tonsillitis, chest pain, high blood pressure, sore throat, intestinal pain and swelling (inflammation), toothache, and water retention (edema).espite serious safety concerns, periwinkle is used for “ brain health” (increasing blood circulation in the brain, supporting brain metabolism, increasing mental productivity, preventing memory and concentration problems and feebleness, improving memory and thinking ability, and preventing early aging of brain cells).