The best defense against a positive drug test is to avoid using drugs in the first place. However, there are a variety of other factors that can influence the results of a drug test. For instance, second-hand exposure to drugs, such as marijuana smoke, can cause a false positive. Similarly, certain medications, such as those used to treat colds and allergies, can also lead to false positives. In addition, some drug tests are more sensitive than others, meaning that they are more likely to detect small traces of drugs. If you are concerned about the possibility of a positive drug test, it is important to talk to your healthcare provider about the best way to protect yourself.