When you or your child has a toothache or canker sore, you might have used Anbesol to help relieve the pain. But, as it turns out, the FDA has warned the medicine with the active ingredient benzocaine could kill you. If used, there’s a potential for developing Methemoglobinemia which reduces the oxygen carried through the bloodstream. You could develop shortness of breath, get blue in the face, and potentially die.