The Christmas custom of kissing under a sprig of mistletoe hung above a door frame or from the middle of a ceiling is known to almost everyone, and many of us will have been willing (or not so willing) participants of this practice at some time. The precise origin of this custom is not clearly understood. The earliest documented case in England is said to date from the 16th century, although one suggestion is that the custom may relate to early beliefs that mistletoe had beneficial effects on fertility and conception.6 Another interpretation is that an exchange of kisses is a promise to marry and a prediction of happiness and long life.5 Allegedly, mistletoe kissing etiquette requires that a man should pluck a berry from the mistletoe branch under which he has kissed a woman and that once the last berry has been plucked, there can be no more kissing. Unwilling potential kissers will already have spotted how this could be used as a get-out clause, but a word of warning: hide the berries, do not eat them. – Courtesy of the Pharmaceutical Journal.