Hello, The fact is, there are a number of different over-the-counter medications, foods, vitamin supplements, and even prescription medicines that can cause a false positive results. Among over-the-counter medicines, many of the night-time cold medications people use to minimize cold and flu symptoms for the evening can cause false positives. This is particularly true of the liquid cold relievers, as many of them contain various members of the ephedrine family. Some weight loss products also can cause false positives, as can some nasal sprays and asthma medications. Certain foods,VIT C and VIT B complex,certain anti biotics like ciprofloxacillin and amoxycillin can sometimes result in a false positive on a drug test. In your case,I feel Vicks inhaler seems to be the culprit. Thanks