This paper explores the social and medical history and context of pink disease (acrodynia), a serious disease of infants and young children that baffled the medical world during the first half of the twentieth century until it was shown to be caused by mercury poisoning. In the English-speaking world the commonest source of the mercury was teething powders, which were widely available and advertised with increasing sophistication. Efforts to control them (such as the BMJ's campaign against 'Secret Remedies') were as yet unsuccessful. The article discusses the social conditions that influenced the existence and recognition of pink disease, the delay in finding its cause, the way in which it was explained as a virus infection or nutritional deficiency and why it seldom occurred outside the teething period. It discusses both professional and lay attitudes to health and diseases during the early twentieth century and provides a model of how the disease developed in a specific social setting and how the medical profession attempted to deal with it within the limitations of contemporary professional thought. The resistance to the evidence of mercury poisoning is typical of resistance to new medical knowledge and declined only when the opponents and sceptics grew old and disappeared from the scene. Meanwhile, the cause having been identified and accepted, pink disease disappeared, but its consequences emerged much later, in an unexpected quarter, as a cause of male infertility.