like a dose of salts
go (right) through (one) like a dose of salts
Of food, drink, or medicine, to be rapidly excreted from the body (as urine or feces) very soon after being ingested. A reference to the use of Epsom salts as a laxative. I try not to drink more than one cup of coffee, it just goes right through me like a dose of salts! I love Indian food, but I eat it so infrequently that when I do, it goes through me like a dose of salts.
like a dose of saltsvery fast and efficiently. British informal
The salts referred to in this expression are laxatives.
1991 Peter Carey The Tax Inspector She's going to go through your old man like a dose of salts.
like a dose of ˈsalts(old-fashioned, British English, informal) very fast and easily: We’ll go through this house like a dose of salts, cleaning it from top to bottom.
Salts in this phrase are laxatives (= medicine that makes you go to the toilet).