I noticed that my antiperspirant has a label that states “Ask a doctor before use if you have kidney disease.” Why is that, and should I be concerned that my daily swipe could be harming my kidneys if I don’t have kidney disease?

The FDA requires the labeling because antiperspirants contain small amounts of aluminum compounds, which could be a potential problem for people with advanced kidney disease if the metal is absorbed. The warning does not apply to healthy people, whose kidneys are able to process aluminum more efficiently, or to people with less severe kidney dysfunction. As the main active ingredient in antiperspirants, aluminum temporarily plugs up sweat ducts to reduce perspiration.

The warning is overly cautious, since there’s no evidence that a significant amount of topically applied aluminum is absorbed. As the National Kidney Foundation states, “It’s almost impossible to absorb enough aluminum through the skin to harm the kidneys.” It quotes a kidney specialist who said, “Unless you eat your stick or spray it into your mouth, your body can’t absorb that much aluminum.”

Moreover, aluminum is widespread in water, soil, and food, and any exposure to aluminum from antiperspirants would be tiny compared to what we typically get from food every day. Buffered aspirin and some antacids also contain aluminum, and people with advanced kidney disease should use them with caution.

Aluminum in antiperspirants does not cause kidney disease (or breast cancer or Alzheimer’s). But if you have kidney disease, do as the label says and ask your doctor if you should avoid antiperspirants. Plain deodorants have no aluminum—but they don’t reduce perspiration.