evidence: A: The vitamin K shot is safe. Vitamin K is the main ingredient in the shot. The other ingredients make the vitamin K safe to give as a shot. One ingredient keeps the vitamin K mixed in the liquid; another keeps the liquid from being too acidic. One of the ingredients is benzyl alcohol, a preservative. Benzyl alcohol is a common ingredient in many medications. In the 1980s, doctors recognized that very premature infants who were in neonatal intensive care units might become sick from benzyl alcohol toxicity because many of the medicines and fluids needed for their intensive care contained benzyl alcohol as a preservative. Although the toxicity was only reported for very premature infants, since then doctors have tried to minimize the number of benzyl-alcohol-containing medications they give. Clearly, the small amount of benzyl alcohol in the vitamin K shot is not enough to be dangerous, even when given in combination with other medications that also contain small amounts of this preservative. [...] The risks of the vitamin K shot are the same risks that are part of getting most any other shot. These include pain or even bruising or swelling at the place where the shot is given. A few cases of skin scarring at the site of injection have been reported. Only a single case of allergic reaction in an infant has been reported, so this is extremely rare.