There are pros and cons to this type of testing.  On the plus side, there is a longer window of detection time since the subject wears the patch for at least seven days and it also serves as an impediment to the person wearing the patch from doing drugs while wearing the patch. Each patch has an identification number encoded on it to prevent substitution of a similar patch. It is quickly and easily removed and the samples can not be diluted like a urine specimen. On the downside the sweat patch can produce false positives because of contamination from external sources.  If there is a residue from any drugs left on the outside of the skin it can be construed as drugs that have been ingested.  Also if the person applying the patch is careless and has not sterilized the area where the patch was placed, this may provide a false positive as well.  With the Sweat Patch, both the “Parent” drug and the drug metabolite can be detected so it gives a better analysis of which drugs can be found in the system.  Some drugs such as heroin and codeine produce the same metabolite so there can be no distinction between which drug was taken, but with the Sweat Patch there can be a certain distinction which drug was used.  The patch must be worn for at least a twenty four hour period before any drugs can be detected and if worn for a seven day period then drugs taken on day one will be detected as well as drugs taken on day seven.  When the patch is removed, it is held up to the light and inspected for any holes that may be present to indicate tampering.  The length of time someone can wear the patch varies but it should not be worn more than fourteen days.  Because the skin has about fifteen to twenty layers and the top layer of the skin is constantly shedding, then the patch can only be worn for a certain length of time.  The adhesive can only hold for a certain amount of time because of the constant shedding of skin.

The patches screen for marijuana, cocaine, opiates, amphetamines/ methamphetamines and PCP.