Sudden sweating and nausea are both symptoms of hyperhidrosis, or excessive sweat. Hyperhidrosis affects approximately 9% of the population. It is most common among women. If you have this condition, it will generally occur at night, when your body does not need to produce energy through activity (such as during sleep). This may be due to a disorder in which nerves do not function normally or because there is an overproduction of certain hormones that lead to excessive sweating. Blocked sweat glands can also contribute to these symptoms by causing continuous wetness under clothes and on skin surfaces where no visible sweat glands exist.