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
Dr. Romanth Waghmarae Dr. Waghmarae. Suboxone: This will show up on a drug test and there are no false positives. No: There is no cross reaction between adhd drugs and opiates. No: I know of no research that shows xenical can cause a false-positive drug test. All xenical does is block some of the fat from your diet from being absorbed, thus decreasing your calorie intake. This shouldn't cause either a urine or a blood drug test to become positive.