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
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.