Goldenseal masks illicit drug use in drug screening tests.

The rumor seems to have gotten started after the book Stringtown on the Pike, written by a pharmacist, was published in 1900. In the novel, a man is discovered "murdered" with traces of a mysterious substance in his stomach.

The substance that investigators thought was strychnine was later identified as goldenseal, which produces the same test reagent color as strychnine.

Even though goldenseal caused a false POSITIVE in the story, many people took this to believe goldenseal could also cause a false NEGATIVE on a drug screening test.