Hello,
Thank you for your query at DoctorSpring.com
I understand your concern.
The ETG test that you're supposed to take, can only detect ethyl gluoronide, a metabolite which comes from alcohol ingestion. A single drop on your arm, won't show anything on the test. Onl if alcohol is consumed in appreciable quantity, then the test turns positive.
So you have nothing to worry about.
Regards.