take something with a pinch of salt
take something with a pinch of saltmainly BRITISH or
take something with a grain of saltmainly AMERICAN
COMMON If you say that someone should take some information with a pinch of salt, you mean that they should not believe it completely because it may not all be accurate or true. Reports from the authorities that the situation is calm should perhaps be taken with a pinch of salt. You have to take these findings with a grain of salt because respondents in attitude surveys tend to give the answers they feel they should. Note: A pinch of salt is a small amount of salt held between your thumb and your first finger. Some people believe that this expression refers to the King of Pontus, Mithridates VI, who lived in the first century BC. It is said that he made himself immune to poison by swallowing small amounts of it with a grain of salt. However, other people think that it is a medieval English expression, which suggests that you need to be suspicious of unlikely stories in the same way that you need salt with food.
take something with a pinch (or grain) of saltregard something as exaggerated; believe only part of something.
1998 Bookseller Meanwhile…readers should take the quotes they see with a pinch of salt.