sick as a dog

*sick as a dog

Cliché very sick; sick and vomiting. (*Also: as ~.) We've never been so ill. The whole family was sick as dogs. Sally was as sick as a dog and couldn't go to the party.
See also: dog, sick

sick as a dog

Very ill, especially from a stomach malady. For example, I don't know what was in that stew but I was sick as a dog all night. This simile was first recorded in 1705. Why a dog should be viewed as particularly sick remains unclear.
See also: dog, sick
References in classic literature ?
When he heard me scraping the ground with it he leaned his forehead against a tree, and was as sick as a dog.