This chapter will focus on primary focal hyperhidrosis henceforth identified simply as hyperhidrosis (HH). The prevalence of HH is reported to be 2.8% although it may be higher. It most commonly presents in the second or third decade of life and a family history has been reported in 30 to 50% of patients ( 13 ). The prevalence is similar for men and women, although interestingly, women are more likely to seek evaluation and treatment ( 11 ). Patients may sweat on a continuous basis throughout the day, but more commonly, there are episodes of profuse sweating with a sudden onset. Trigger factors include emotional stress, stress at work or in the public, higher environmental temperatures, and stimulants such as caffeine and exercise. However, patients also often have episodes of HH without a known initiating factor or trigger when they are cool, comfortable, and calm.