Just because cough drops are sold in the medicine aisle doesn't mean they're healthy. Most are loaded with sugar. So after soothing your throat with a lozenge, be sure to brush well. Whether the sugar comes from a cough drop or a hard candy, it reacts with the sticky plaque that coats your teeth. Then bacteria in the plaque convert the sugar into an acid that eats away at tooth enamel. Hello, cavities.