For the second year in a row, the US has surpassed 25,000 whooping cough cases — another sign of the risks of falling vaccination levels.

Vitamin C toxicity is rare, but daily doses over 2,000 milligrams may cause unpleasant side effects like digestive issues, headache, and skin flushing.

Ascorbic acid, the scientific name for vitamin C, supports immune function. Eating ascorbic acid-rich foods helps your immune system work properly.