Alcohol withdrawal occurs when a person who is accustomed to drinking large amounts of alcohol suddenly stops drinking alcohol. Alcohol withdrawal symptoms usually are most severe after 48 to 72 hours, but they can persist for weeks. A severe form of alcohol withdrawal is called delirium tremens (DT). Symptoms of alcohol withdrawal can include depression, anxiety, fatigue, nervousness, nightmares, jumpiness, mood swings, insomnia, and nausea and vomiting. Other symptoms can include sweating, tremor, pallor, rapid heart rate, headache, and dilated pupils. Symptoms of DT are more severe and may consist of seizures, fever, hallucinations, confusion, and agitation. DT may also cause fear, delirium, decreased attention span, and other changes in mental function.