More on Masquerade Balls

The first documented evidence of Masquerading (the wearing of masks as disguise), in Venice dates back to 2nd May 1268 and pertains to a decree forbidding masqueraders to practice the game of 'the eggs' - the throwing of 'scented' eggs at the ladies of the court. The anonymity of the masked throwers, the reference to 'scented' - surely meaning 'bad eggs', and the fact that a decree had to be made at all, appears to indicate that the fun was a one way thing with the Egg game.
 
Masquerade Balls were first noted in Italy, particularly in Venice, during the 15th century Renaissance. A Masquerade Ball, Bal Masqué, or 'Masque' was a formally staged pageant event, with formal dancing and musical performances. Hosted by members of the upper and elite classes, to celebrate events such as marriages, guests attended in elaborate costume including a mask – providing a temporary anonymity which served to release them from the strict social conventions of their class. Entirely disguising each guest's identitity, added an often flirtatious 'guessing game' aspect to Masquerade Balls, introducing an element of excitement to an otherwise ordinarily tedious formal occasion.
 
Masquerade balls became common throughout mainland Europe in the 17th & 18th centuries. A Swiss Count, John James Heidegger, is credited with having introduced the Venetian fashion of a semi-public masquerade ball to London in the eighteenth century, with the first of these events being held at Haymarket Opera House.