Legal and illegal drugs that will confuse a drug test at probation?

There is an extremely long list of licit drugs that look like illicit drugs to some drug tests. Poppyseeds will look like opiates (probably since they have opiates in them), most of the new pain relievers like naproxen and ibuprofen look like weed, and Alka-Seltzer looks like speed.

Use http://www.askdocweb.com/falsepositives.html to see what crosses with what.