Excessive underarm sweating is also known as hyperhidrosis and is caused when the eccrine sweat gland produces far more sweat that the body actually needs, which can cause distress and embarrassment in social situations. A simple and effective treatment for excessive sweating is Botulinum treatment, which can block the action of the nerves that supply the sweat glands. The effect of just one treatment can last several months or even up to a year.