Following early confusing but dramatic case reports of severe systemic reactions to parenteral vitamin K there has been a persistent and widely promulgated notion that it causes anaphylaxis.
In a recent article in Emergency Medicine News Dr. James Roberts critically examines this claim and attempts to make sense of the evidence. He concludes that there is reason for caution although the mechanism of the reaction, the degree of risk and any relation to prior vitamin K exposure is unclear. Although the problem may be overblown there is likely some risk. Oral vitamin K appears to be safer and should be used when possible.