Taken from Erowid. It's NOT illegal...so I have no idea why it would matter if it showed up or not. How hard would it be to explain? "Oh yeah, mom I took some cough syrup earlier this week." Wtf.
DXM may cause false positives for both PCP and Opiates in standard urine tests.- erowid I assume a hair test wouldn't be different?
If it did happen to cause a false positive, then all they would have to do is send it to a lab to do more extensive testing to rule out the false positive.
I think you will be fine as long as you didnt puff herb. Just let em know you like to drink cough syrup for fun. Your already in trouble young man.
its pretty unlikely to cause a false postive for opiates but is very similar chemichaly to pcp so a pcp false positive isnt that unlikely