250ml of wine causes the body to expel 800 to 1,000ml of water. That's four times of the liquid losts from the body than gained. No wonder that the morning after heavy drinking, the body sends a message to replenish its water supply. Headache is one of the symptoms of hangover which results from dehydration. Because of this now the body's organs try to make up for their own water loss by stealing water from the brain, "This makes the brain decrease in size and pull on the membranes that connect the brain to the skull."