The sweat patch consists of an absorbent pad held in place by a strong adhesive film. If a person uses drugs while wearing the patch a small amount of the drug and drug metabolites is excreted in the sweat. The sweat patch absorbs the sweat and traps the drug and drug metabolites in the sweat. The patch is analyzed at a laboratory for the presence of six drugs: Cocaine, marijuana, opiates, amphetamines, methamphetamines and PCP.
The adhesive film protects the patch from environmental contamination. Any attempts by the subject to tamper with, adulterate, or remove and re-apply the patch leave visible signs that can be detected by a trained collector. This makes the sweat patch one of the more difficult drug testing methods to defeat.