Various methods may apply iodine on a test area of a subject and allow the applied iodine to dry. Sweating may be triggered in the test area. Triggering sweating may include introducing acetylcholine (ACh) using iontophoresis into dermis within an iontophoresis area. An indirect response to introduction of the ACh may be monitored. Monitoring the indirect response may include applying starch tape over the iodine-painted test area to monitor sweat production from individual sweat glands (SGs) outside of the iontophoresis area, wherein sweat production for each functional SG results in a sweat spot on the starch tape, and taking a series of digital images, using a digital camera, of the starch tape when the individual SGs are producing sweat and causing sweat spots on the starch tape. The digital images of sweat spots may be analyzed to analyze sweat production from the individual SGs.
