Certain antibiotics (like Amoxicillin) are claimed to cause a positive for heroin or cocaine. My expert source was unable to verify this, so I regret that there is some uncertainty here.
Some legal products actually contain small amounts of illegal chemicals. All tests, including the GC/MS, will test you positive because the metabolites derived from the true positive are identical to the metabolites of the illegal drugs.
Detox products are drinks, pills, or effervescent…