The seven-year itch is the tendency for a married person to flirt with infidelity after seven years of marriage. The beginning of the use of the phrase the seven-year itch to mean the inclination of a person to stray after seven years of marriage can be traced directly to the play of the same name written by George Axelrod in 1952. Before this time, the seven-year itch was an American phrase that described an actual physical condition. This condition was a rash caused by a bacterial infection known as scabies. Scabies was extremely difficult to get rid of, which made it seem as if it lasted seven years. Today, it is very easy to treat. George Axelrod borrowed the term to describe the tendency for a person to be unfaithful after seven years of marriage. The play became a movie starring Marilyn Monroe and Tom Ewell, and the meaning of the seven-year itch changed drastically. When referring to the play or movie, the term is rendered without a hyphen as in The Seven Year Itch, when referring to the phenomenon of marital infidelity, the term is hyphenated, as in seven-year itch.
He added: “[The risk of divorce] just steadily declines as we get used to each other. It’s a four-star statistic, the seven-year itch.” (The Cape Times)
Lu Guoping wrote on Weibo, China’s version of Twitter, that marriage certificates should only be valid for a limited time as many couples cannot get through the “seven-year itch” in a relationship when the initial strong attraction supposedly starts to wane. (The South China Morning Post)