Sweat Halo

Axon reflex response to 6mm diameter ACh stimulation

Figure 1.  Sweat halo due to axon reflex response from 6 mm stimulation with ACh.

Sweat halo pattern around stimulation

Figure 2.  Sweat halo pattern around 1 mm stimulation site captured with starch coated sheet (left) and MATLAB analysis (right).

Graph showing sweat halo radii distribution.

Figure 3.  Histogram of radii lengths from halo sweat pattern.

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Iontophoresis of acetylcholine (ACh) is used to directly stimulate the sweat glands in a small area of skin.  Neighboring glands then begin to produce sweat via the axon reflex response of the peripheral nerves near the stimulation site.

The skin is coated with iodine and then a starch-coated sheet is applied to capture a snapshot of sweat distribution (Figure 1).

The sweat region count, sizes and distance from the stimulation site are calculated using MATLAB image processing and used to grade the innervation of the test site (Figure 2).