Even the ever-inventive Agatha Christie did not see mayonnaise as a murder weapon. But the Tamil Nadu government views the sauce with suspicion because unsafe mayonnaise used in shawarma has sent several people in the state to the hospital; this week, the government extended its ban on the emulsion by a year. The bacterium that makes it hazardous—salmonella—is so common in India that a dedicated research centre for it was established in Kasauli in 1958. Recent outbreaks have been noted in Kerala, Maharashtra and Delhi, mostly because of contaminated poultry products or milk. Food bans are not easy to digest. But Tamil Nadu’s move is a timely reminder that we are again in the season when edibles go bad quickly and extra caution is required for street food.