Dialated pupils

My 17 year old son has had dialated pupils for the last couple days.  I noticed this once before on him.  I have pointed this out to him, and he is defensive and denies using any drugs.  This is causing stress between us.  Could there be a medical cause besides drug use?  If he used drugs one day, could it cause his pupils to be dialated for several days?  What kind of recreational drug would cause this?  I do not find any other signs of drug use, except his eyes looked puffy the first night I noticed it after he had been at a friend's house.  Are there tests at the doctor's that could detect use of ecstacy?

[John C Hagan III, MD, FACS, FAAO]

There are some young people that have large pupils all the time. Sudden increase of size assuming they are equal in size and do react to light and focus certainly raises the possibility of illegal drug use. A variety of drugs can dilate the pupil and certain legal medicines that are taken for a "buzz" can alsol Iexample pseudoephedrine.

Your family physician can order a toxological exam of urine that will pick of many of the commonly used illegal drugs.

JCH III MD