When your doctor prescribes a medication, they take care not to give you something that might cause harm. But, many drugs have a hidden danger for people with allergies or other sensitivities. The inactive ingredients, non-drug components of a medication, can contain compounds that cause harm. And, says a new study, many doctors don’t even know what those ingredients are.

It’s not really a doctor’s job to know the exact formulation of every medication they give out, of course, especially