To answer this question without understanding the peculiar anatomy of the sympathetic chain will be very difficult for the layperson to understand. Basically speaking, variation in the amount of dryness can happen a short time or very long time after ETS was done. Variations in the anatomy of the sympathetic chain can happen among different patients as well as within the same person. This means that the patient after having ETS can experience at times for dampness or mild sweating at different times of the year but the overall dryness of the hands is kept. As far as we know the reason for that, stems from the fact that the original cells of the sympathetic chain is within the spinal cord. Very few anatomical studies have been done on spinal cords of patients with hyperhidrosis to come to any definite explanation for those clinical changes in the amount of dryness in their hands.