What the research says

Here's what the research shows about zinc that's taken by mouth for the following conditions:

• Zinc deficiency. People who have low levels of zinc seem to benefit most from zinc supplements. Zinc deficiency isn't common in the United States. But some medicines, such as thiazide diuretics taken to treat high blood pressure, can raise the amount of zinc lost in urine. That could lead to zinc deficiency.
• Colds. Research suggests that if zinc syrup or lozenges are taken within 24 hours after cold symptoms start, zinc can help shorten the length of a cold. But the use of zinc that's placed into the nose, called intranasal zinc, has been linked to loss of the sense of smell. Sometimes, the loss of smell may last for a long time. And it's possible that the sense of smell may not come back at all.
• Wound healing. People who have wounds such as skin ulcers and who also have low levels of zinc might benefit from taking a zinc supplement by mouth.
• Diarrhea. Zinc supplements can ease symptoms of diarrhea in children who have low levels of zinc. That may happen in children who have malnutrition. There isn't enough research to recommend use of zinc supplements for children with diarrhea who eat a healthy, varied diet.
• Age-related macular degeneration. Research suggests that zinc supplements taken by mouth might slow the progression of this eye disease.

Zinc that's used on the skin is called zinc oxide. Zinc oxide cream, ointment or paste is put on the skin to prevent conditions such as diaper rash and sunburn.