The growing toll of popular fallacies about health and illness is evident given outbreaks of measles and other preventable communicable diseases in many nations. This “medical misinformation” phenomenon has been described as “a health-related claim of fact that is currently false due to a lack of scientific evidence,”1 but that may be a generous interpretation. Complementary and alternative medical approaches, without firm evidentiary bases, have coexisted uncomfortably with mainstream scientific medicine for decades, and they persist.2 By contrast, contemporary misinformation of greatest concern is supplanting well-proven interventions and ideas with unproven ones that are clearly false and, in some cases, harmful.