Cold sores are caused by the herpes simplex type 1 virus and are contagious whereas canker sores are not. Also, cold sores can appear outside the mouth in places such as under the nose, on the lips or under the chin while canker sores always appear inside the mouth.anker sores, or aphthous stomatitis, are small ulcers in your mouth that cause pain and discomfort when talking or eating. Canker sores come in two varieties: simple and complex.
Codeine, which is found in many pain relievers, may cause a false positive for morphine or heroin because of its similar chemical structure. Antibiotics. Certain newly developed antibiotics including amoxicillin and ampicillin have been reported to cause false positives for cocaine. DHEA
Always Test Clean has assembled the most comprehensive list of what can cause a false positive drug test. Search a list of foods, medications and prescriptions that can cause a false positive drug test by name.The following is a list of medications, prescriptions and other things that can cause a false positive drug test cross referenced to the type of drug test you can expect to be at risk for passing a drug test.here are no major products that can cause a false positive drug test that begin with âJâ. K. 1  Klonopin â Contains Benzodiazepines. 2  Koalin Or Morphine Mixture â Can Cause False Positives For Opiates.