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If he has taken a couple of doses of OTC anti-allergy medicine a week back, they will not show up on the screening test
For starters it is quite uncommon for OTC allergy medicines to produce a false positive in drug test,
also most importantly, even if the screen is positive, a confirmatory GC/MS test can easily confirm the presence/ absence of a drug in the system
So, I would recommend that he write the name of the OTC drug that he took on the test form, and does not worry about the test, since a confirmatory test will clearly show the absence of any drugs, even in the rare chance that the screening test comes positive,
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