While proofreading The Life and Times of Francis the First, King of France I came across this interesting little snippet:
At the commencement of the year 1521, an accident happened which had nearly deprived France of her monarch, and removed from Charles's path the greatest obstacle to the accomplishment of his ambitious projects. The court passed the Christmas at Romorentin; on the Twelfth Night, the count de St. Pol had given an entertainment, at which the old custom of choosing a Roi de la Fêve was practised. The king, who was the very soul of mirth in his jocund court, proposed that a party should go and attack this mock monarch at the hotel of the count de St. Pol. A formal challenge was sent, and a defiance returned. The count de St. Pol and his friends collected arms and ammunition to repel their assailants, and their weapons consisted of snow-balls, hard eggs, and baked apples. The fight was kept up with great spirit on both sides; at length, the ammunition of the besieged was expended, and the assaulting troops were forcing the doors. At this moment one of the persons in the hotel very imprudently threw a lighted firebrand from one of the windows, which struck the king on the head. The injury he received was so serious, that for some days his life was despaired of. It was generally reported that he was dead; and even those about him believed he had lost his eye-sight. Francis displayed, upon this occasion, that goodness of heart which commonly distinguished him. He desired particularly that no inquiry should be made for the person by whom the brand had been thrown. It is altogether my own fault, he said. I committed the first folly: and it is fit that I should bear the pain of it.
This accident gave occasion to a change in the fashion. It had been for many years the custom to wear the hair extremely long, and the beard quite short. Francis, who had been obliged to have all his hair cut off in consequence of the hurt he had received, adopted the Italian and Swiss fashion of wearing his hair short and his beard long, and continued this habit during his life. It was, of course, followed by his court, and soon came to be generally adopted.
And, in the accompanying footnote, the author elaborates:
The common people, who are slow to change their old customs, continued the former practice of wearing their hair and shaving their beards; and members of the legal and other grave professions did not adopt the change. It soon became so much an exclusive distinction of their body, that the celebrated Olivier de Duville, who was afterwards chancellor, was refused admission to the sittings of the parliament in his office of maître des requêtes, unless he would cut off his beard. The university of Paris, in 1534, interdicted masters of arts from wearing their beards.
Looking for some pictorial evidence of this change I found these contrasting images of Francis.
The first (from expositions.bnf.fr) is his portrait on a gold double ducat, dated from 1515-1516.
The second (from photo.rmn.fr) is a wax medallion dated to the second part of the sixteenth century, so was produced posthumously, either by someone who knew him or by working from a portrait from the later part of his life.
There are portraits of Francis done during his life, which show the shorter hair and longer beard, the contrast is there, but less pronounced.
See Francis the First, King of France