Pounding headache, dry mouth, red eyes, fuzzy memory — the pain of a hangover is familiar to many. But why does alcohol make us feel so good and then so bad? Even though human beings have suffered from hangovers for thousands of years, we're still largely in the dark as to exactly why they happen, and how to cure them. Researchers say many hangover cures simply don't work. The only sure-fire cure, they say, is not to get drunk in the first place. If only it were that simple. Here is what scientists believe takes place in the body after a big night out on the town.

Headache: Scientists believe that those throbbing, relentless hangover headaches are due to a number of factors. The first is dehydration. Alcohol prevents the release of a hormone responsible for retaining water in the body. As a result, the kidneys no longer conserve water and more fluid is excreted as urine. Moreover, alcohol widens the blood vessels in the head, adding to the pain.

Concentration: Avoid any task that requires more than half your brain. Studies suggest that hangover misery interferes with both short-term memory and concentration. One study of military pilots revealed that flying ability was still impaired eight to 14 hours after drinking, especially in older pilots. Some studies suggest that dehydration might be to blame, while others believe that acetaldehyde, a product of alcohol breakdown, may have an impact, along with sleep deprivation. Despite alcohol sending us to sleep, it worsens the quality of our shuteye, leaving people incredibly tired in the morning.

Click here to learn how to make 'Hangover-Free Cocktails'

Mood: The world is usually not a happy place when you awake after a big night. Hangovers increase depression, anxiety and irritability. Scientists are still unsure exactly how alcohol exerts its mind-bending affects, but believe that it is a combination of sleep deprivation, a lack of serotonin — a mood-enhancing chemical in our brain — and an alcohol-induced drop in blood sugar. And the dizziness and light-headedness? Also due to dehydration, say researchers.

Eyes: A telltale sign of a heavy night, eyes become puffy, sore and bloodshot. Alcohol causes blood vessels in the eyes to dilate and dehydration leaves them feeling dry.

Mouth: The mouth and throat feel dry, furry and generally disgusting. This is caused by dehydration and is worsened by smoking.

Nervous system: As anyone knows who has passed out after a night of drinking knows, alcohol is a sedative. But to make sure that we don't slip into unconsciousness, our nervous system steps up a gear and becomes more alert. When the alcohol leaves our body, however, the nervous system remains in a hyperactive state, leading to sweating, shaking and sensitivity to light, sound and touch. Further, sleep deprivation can aggravate these symptoms.

Heart: Heart rate increases, possibly as a result of alcohol interfering with the body's nervous system. Long-term alcohol abuse can lead to cardiomyopathy — damage to the heart muscle.

Liver: Alcohol cannot be stored in the body and so is broken down in the liver. In this two-step process, alcohol is turned into acetaldehyde, which then becomes acetate. However, this process is slow — one unit of alcohol is metabolized every hour. It is widely believed that acetaldehyde may contribute to the misery of the hangover, as accumulation in the blood causes rapid pulse, sweating, skin flushing, nausea and vomiting. Some people lack a molecule that breaks down this compound and become ill soon after drinking. Further, alcohol metabolism leads to an accumulation of fatty compounds in the liver and lactic acid in the body fluids. These inhibit glucose production, leading to low blood sugar.

Body temperature: Ever felt a bit hot under the collar when you're suffering with a hangover? Alcohol may interfere with the production of hormones that control the 24-hour body clock, leading to body temperature being abnormally high.

Stomach: Alcohol irritates the stomach lining and delays it emptying, leading to nausea and vomiting.

Muscles Everything is an effort when you have a hangover. Muscle weakness and general fatigue are a result of low blood sugar and dehydration. The latter, together with an accumulation of lactic acid from alcohol metabolism, can cause foot and leg cramps.

Click here to read more on this story from the Times of London and to learn how to alleviate some of the pain of a hangover.