A masked reveller parades through the streets on the first day of the carnival season in Lucerne, Switzerland, 12 February 2015. In the background the well known Kappellbruecke bridge. (Photo by Alexandra Wey/EPA)

A girl wearing a mask takes part in a procession celebrating the religious holiday of Mawlid al-Nabi, the birthday of Prophet Mohammad, in Benghazi, Libya December 10, 2016. (Photo by Esam Omran Al-Fetori/Reuters)

A young boy adjusts his friend's Adolf Hitler mask during a game on a street in King's Cross, London. (Photo by William Vanderson/Getty Images). 1938

A man with a mask poses for a portrait as he takes part in festivities in honour of patron saint San Jeronimo in Masaya city, Nicaragua November 20, 2016. (Photo by Oswaldo Rivas/Reuters)

A man wearing a mask and dressed in a clown costume rides an electric tricycle while carrying a container in the shape of a rubber duck amid heavy smog in Beijing, China, December 29, 2015. (Photo by Jason Lee/Reuters)

A woman and her dogs stop and look at a store mannequin wearing a dog's head mask outside a fashion shop in Nice, France, May 3, 2016. (Photo by Eric Gaillard/Reuters)

A masked reveller poses near Saint Mark's Square during the Venetian Carnival in Venice January 31, 2015. (Photo by Stefano Rellandini/Reuters)