How Hangovers Work

More than 75 percent of alcohol consumers have experienced a hangover at least once.

­It's no secret that intoxication has a number of immediate negative consequences. Among other things, it impairs judgment, it impairs the ability to do most things and it can bring on a depressed mood. But even after a drinker has sobered up, alcohol can still be causing the body trouble. More than 75 percent of alcohol consumers have experienced a hangover at least once; 15 percent have one at least every month; and 25 percent of college students feel symptoms weekly.

In this article, we'll explain what causes hangover symptoms and examine the science of the popular prevention methods and morning-after remedies.


What is a Hangover?

­The formal name for a hangov­er is veisalgia, from the Norwegian word for "uneasiness following debauchery" (kveis) and the Greek word for "pain" (algia) -- an appropriate title considering the uncomfortable symptoms experienced by the average drinker. The common hangover includes some or all of the following:

  • Poor sense of overall well-being
  • Headache
  • Sensitivity to light and sound
  • Diarrhea
  • Loss of appetite
  • Trembling
  • Nausea
  • Fatigue
  • Increased heart rate and blood pressure
  • Dehydration(dry mouth, extreme thirst, dry eyes)
  • Trouble concentrating
  • Anxiety
  • Difficulty sleeping
  • Weakness

­The most common symptoms are headache, fatigue and dehydration, and the least common is trembling. The severity and number of symptoms varies from person to person; however, it is generally true that the more alcohol a drinker consumes, the worse the hangover will be.


It usually takes five to seven cocktails over the course of four to six hours to cause a hangover for a light-to-moderate drinker (a man who drinks up to three alcoholic beverages a day or a woman who drinks up to one). It may take more alcohol for heavier drinkers because of increased tolerance. Other than the number of drinks consumed, hangovers can be made worse by:

  • Drinking on an empty stomach
  • Lack of sleep
  • Increased physical activity while drinking (dancing, for example)
  • Dehydration before drinking
  • Poor health

The reason for some symptoms isn't fully understood, but research has led scientists to have a pretty good understanding of the primary causes of a hangover. In the next sections, we'll find out what's going on in the body to cause these problems.

Biology of a Hangover: Vasopressin Inhibition

W­hen alcohol is consumed, it enters the bloodstream and causes the pituitary gland in the brain to block the creation of vasopressin (also known as the antidiuretic hormone). Without this chemical, the kidneys send water directly to the bladder instead of reabsorbing it into the body. This is why drinkers have to make frequent trips to the bathroom after urinating for the first time after drinking.

According to studies, drinking about 250 milliliters of an alcoholic beverage causes the body to expel 800 to 1,000 milliliters of water; that's four times as much liquid lost as gained. This diuretic effect decreases as the alcohol in the bloodstream decreases, but the aftereffects help create a hangover.


The morning after heavy drinking, the body sends a desperate message to replenish its water supply -- usually manifested in the form of an extremely dry mouth. Headaches result from dehydration because the body's organs try to make up for their own water loss by stealing water from the brain, causing the brain to decrease in size and pull on the membranes that connect the brain to the skull, resulting in pain.

­The frequent urination also expels salts and potassium that are necessary for proper nerve and muscle function; when sodium and potassium levels get too low, headaches, fatigue and nausea can result. Alcohol also breaks down the body's store of glycogen in the liver, turning the chemical into glucose and sending it out of the body in the urine. Lack of this key energy source is partly responsible for the weakness, fatigue and lack of coordination the next morning. In addition, the diuretic effect expels vital electrolytes such as potassium and magnesium, which are necessary for proper cell function.

Different types of alcohol can cause different types of hangover. In the next section, we'll look at the differences.

Biology of a Hangover: Congeners

Dark wines and liquors have higher levels of certain toxins.

Different types of alcohol can result in different hangover symptoms. This is because some types of alcoholic drinks have a higher concentration of congeners, byproducts of fermentation in some alcohol.

The greatest amounts of these toxins are found in red wine and dark liquors such as bourbon, brandy, whiskey and tequila. White wine and clear liquors such as rum, vodka and gin have fewer congeners and therefore cause less frequent and less severe hangovers. In one study, 33 percent of those who drank an amount of bourbon relative to their body weight reported severe hangover, compared to 3 percent of those who drank the same amount of vodka.


Because different alcoholic drinks (beer, wine, liquor) have different congeners, combining the various impurities can result in particularly severe hangover symptoms. Additionally, the carbonation in beer actually speeds up the absorption of alcohol. As a result, following beer with liquor gives the body even less time than usual to process the toxins.

Biology of a Hangover: Acetaldehyde

A product of alcohol metabolism that is more toxic than alcohol itself, acetaldehyde is created when the alcohol in the liver is broken down by an enzyme called alcohol dehydrogenase. The acetaldehyde is then attacked by another enzyme, acetaldehyde dehydrogenase, and another substance called glutathione, which contains high quantities of cysteine (a substance that is attracted to acetaldehyde). Together, the acetaldehyde dehydrogenase and the glutathione form the nontoxic acetate (a substance similar to vinegar). This process works well, leaving the acetaldehyde only a short amount of time to do its damage if only a few drinks are consumed.

Unfortunately, the liver's stores of glutathione quickly run out when larger amounts of alcohol enter the system. This causes the acetaldehyde to build up in the body as the liver creates more glutathione, leaving the toxin in the body for long periods of time. In studies that blocked the enzyme that breaks down acetaldehyde (acetaldehyde dehydrogenase) with a drug called Antabuse, designed to fight alcoholism, acetaldehyde toxicity resulted in headaches and vomiting so bad that even alcoholics were wary of their next drink. Although body weight is a factor (see How Alcohol Works), part of the reason women should not keep up with men drink-for-drink is because women have less acetaldehyde dehydrogenase and glutathione, making their hangovers worse because it takes longer for the body to break down the alcohol.


Some of the most common hangover symptoms -- fatigue, stomach irritation and a general sense of illness all over -- can be further attributed to something called glutamine rebound. In the next section, we'll see what this aftereffect is all about.

Biology of a Hangover: Glutamine Rebound

After a night of alcohol consumption, a drinker won't sleep as soundly as normal because the body is rebounding from alcohol's depressive effect on the system. When someone is drinking, alcohol inhibits glutamine, one of the body's natural stimulants. When the drinker stops drinking, the body tries to make up for lost time by producing more glutamine than it needs.

The increase in glutamine levels stimulates the brain while the drinker is trying to sleep, keeping them from reaching the deepest, most healing levels of slumber. This is a large contributor to the fatigue felt with a hangover. Severe glutamine rebound during a hangover also may be responsible for tremors, anxiety, restlessness and increased blood pressure.


Because alcohol is absorbed directly through the stomach, the cells that line the organ become irritated. Alcohol also promotes secretion of hydrochloric acid in the stomach, eventually causing the nerves to send a message to the brain that the stomach's contents are hurting the body and must be expelled through vomiting. This mechanism can actually lessen hangover symptoms in the long run because vomiting gets rid of the alcohol in the stomach and reduces the number of toxins the body has to deal with. The stomach's irritation may also be a factor in some of the other unpleasant symptoms of a hangover, such as diarrhea and lack of appetite.

So now we know why alcohol causes hangovers. In the following sections, we'll look at the science behind the most common hangover "cures."

Food and Drink Remedies - Fact or Fiction?

Burnt toast or drinking a little more alcohol the next day won't do a lot for a hangover.
© Allfree

Hangover remedies include everything from "a hair of the dog that bit you" (drinking a little more alcohol the next morning), to burnt toast and black coffee to an over-the-counter product like Chaser. Which of all the endless theoretical remedies actually have truth behind them?

Hair of the Dog

Contrary to popular belief, more of the "hair of the dog that bit you" only delays the inevitable. One of the reasons hangovers are so unpleasant is the liver is still processing the toxins left over from alcohol metabolism. Drinking more alcohol can make the symptoms seem to lessen at first but will only make the situation worse once the liver breaks the alcohol down, because it will have even more toxins to deal with.



  • FICTION - Remedy

Burnt Toast

At first, the burnt toast remedy may seem that it's actually based on scientific fact. The culprit behind this fictional cure is the carbon in the charred bread. Carbon can act like a filter in the body. While it's true that activated charcoal (which is a treated form of carbon) is used to treat some types of poisonings, it's not currently used to treat alcohol poisoning (something that is vastly different from a regular hangover).

The carbon/charcoal found on burnt toast is not the same as activated charcoal.


  • FICTION - Prevention and Remedy

Black Coffee

Coffee contains a high amount of caffeine, which is a stimulant and therefore helps fight fatigue. But when the caffeine wears off, a drinker may be even more tired than before. Coffee can help alleviate a pounding head because caffeine is a vasoconstrictor, meaning it reduces the size of blood vessels. This counteracts the effect of the alcohol, which makes them swell, making the head hurt in the first place. Unfortunately, caffeine is also a diuretic like alcohol and can make a drinker even more dehydrated than before, thereby increasing the severity of the hangover. Overall, coffee isn't a good hangover cure.


  • FICTION - Remedy

Fried or Fatty Foods

Although eating fried or fatty foods the morning after will probably only irritate a drinker's stomach further, eating them before drinking can actually be helpful. Putting anything in the stomach prior to indulging in alcohol helps prevent a hangover, but fatty foods in particular stick to the stomach lining longer and therefore slow down the absorption of alcohol into the bloodstream. While that might make it take longer to feel the alcohol's effects, it also gives the body more time to process the byproducts and will increase a drinker's chances of feeling decent in the morning. So much so, in fact, that a Mediterranean folk tactic is to take a spoonful of olive oil before drinking alcohol. Eating lighter food such as a fruit smoothie will provide energy and alleviate some symptoms by replenishing the electrolytes the body lost from dehydration.


  • FACT - Prevention
  • FICTION - Remedy


Eating eggs the morning after provides energy like any other food, which is the primary benefit. But eggs do also contain large amounts of cysteine, the substance that breaks down the hangover-causing toxin acetaldehyde in the liver's easily depleted glutathione. Therefore, eggs can potentially help mop up the left-over toxins.


  • FACT - Remedy


Eating bananas the morning after a night of heavy drinking provides lost electrolytes like any food would, but it also specifically replenishes the potassium lost to alcohol's diuretic effect. Other potassium-rich foods such as kiwi fruit or sports drinks work just as well.


  • FACT - Remedy


Replenishing the body's water supply after a night of drinking combats dehydration, and it also helps dilute the leftover byproducts in the stomach. Adding salt and sugar to water helps replace the sodium and glycogen lost the night before. Non-caffeinated, non-carbonated sports drinks can achieve the same effect.

As a prevention method, drinking a glass of water for every alcoholic beverage slows down drinking, providing more time for the body to deal with the alcohol (the body can only process about three-quarters of an ounce of alcohol in an hour). Drinking a few glasses of water before going to bed helps fight dehydration after the body finishes breaking down the alcohol.


  • FACT - Prevention and Remedy

Fruit Juice

­The fructose -- fruit sugar -- in fruit juice helps to naturally increase the body's energy. Studies have proven that it also increases the rate at which the body gets rid of toxins such as those left over from alcohol metabolism. Fruit juice is also a good idea the morning after because it's high in vitamins and nutrients that were depleted the night before because of alcohol's diuretic effect. Vitamin supplements high in vitamins C and B are also effective.


  • FACT - Remedy


Other Remedies - Fact or Fiction?


Certain painkillers are more effective at combating a hangover than others. For instance, Excedrin can be helpful for a headache because it combines acetaminophen for the pain and caffeine to reduce the size of the pounding blood vessels; however, prolonged combination of alcohol and acetaminophen has been shown to cause liver damage, and caffeine is a diuretic.

Aspirin is a non-caffeinated pain reliever and is also in a class of anti-inflammatory drugs known as prostaglandin inhibitors. High levels of prostaglandin have been associated with increased hangover severity. In one study, participants who took a prostaglandin inhibitor before bed reported less of a headache and less nausea and thirst than those who had drank the same amount of alcohol but did not take the prostaglandin inhibitor before bed. If you have a sensitive stomach, though, beware -- taking aspirin after drinking can make your stomach hurt even worse.



  • FACT - Prevention and Remedy if non-caffeinated and acetaminophen-free

Over-the-counter Remedies

Hangover remedies such as Chaser, Sob'r-K Hangover Stopper, RU-21, Berocca and Rebound are highly varied both in price and ingredients, so their effectiveness varies accordingly. They're classified as dietary supplements, meaning:

  • They contain vitamins and minerals.
  • They don't require a prescription.
  • They're usually taken in pill form.

The manufacturers claim these products work because they make use of the effective filtering qualities of carbon to reduce the number of impurities the body has to process (see "Burnt Toast" in the last section for the science on that one). As for RU-21, marketed as a secret KGB pill, the manufacturer says specifically that it is not an anti-hangover pill but a supplement for detoxification. (By the way, its main ingredients -- dextrose, L-Glutamine and vitamin C -- can be found in high amounts in everyday foods). Rebound has the same ingredients as RU-21 plus a few other vitamins and oddities such as "young barley grass juice powder," but it's still basically a multivitamin. Berocca, again, is not a hangover cure -- it's simply a multivitamin that claims to increase energy naturally (through vitamins).

The secret to most of these purported "miracle cures" may in fact be the amount of water a drinker ingests when taking them. Many require taking a pill (or two) with a glass (or two) of water before drinking alcohol, and then continuing to take the pills over the course of the evening with full glasses of water, before bed with a full glass of water, and upon waking with a full glass of water. The hydration alone greatly improves the chances of having little-to-no hangover, and the vitamins in the pills just give it a little, albeit expensive, boost.


  • FICTION - Prevention and Remedy 


The only complete cure for a hangover is time. No matter what a drinker does, the body still has to clean up all the toxic byproducts left over from the evening before. But the above factual remedies can help speed up the process.


  • FACT - Remedy

Hangover Remedy Overview


­The only fool-proof way to avoid a hangover, of course, is not to drink alcohol. But from a scientific perspective, researchers have found the following general regimen minimizes the symptoms of a hangover.


Before Drinking

  • Eat a full meal - A full stomach slows down the absorption of alcohol, giving the body more time to process the toxins. Fatty foods and carbohydrates increase this effect. Having food in the stomach also decreases stomach irritation, in turn reducing the likelihood that a drinker will vomit.
  • Drink a glass of water - This ensures the body is hydrated before the diuretic effect takes hold.
  • Take multivitamins - This better prepares the body for the depletion of vitamins caused by frequent urination.

While Drinking

  • Drink in moderation - Ideally, drinkers should limit themselves to one drink per hour because the body takes about an hour to process a single drink.
  • Drink a glass of water after every alcoholic beverage - In addition to helping keep a drinker hydrated, this will give the body more time to process the alcohol, dilute the toxins and reduce irritation of the stomach. A sports drink like Gatorade or Propel will also replenish electrolytes, salts and sugars lost in the urine.
  • Watch your drink choice - Drinkers generally fare better when they stick with one drink. Each new type of alcohol a drinker puts into his or her system makes the body work that much harder and puts that many more toxins in the body, leading to a more severe hangover. Here's a rundown of the major types of alcohol and their effects: Beer has the lowest percentage of alcohol (4 to 6 percent), but it's also carbonated, which speeds up the absorption and can lead to toxin buildup. Wine has a higher percentage of alcohol (7 to 15 percent) than beer, but it's usually not carbonated. White wine is safer than red or blush because it has fewer congeners. In general, the cheaper the wine, the higher the congener content and the worse the hangover. Liquor has the highest alcohol content (40 to 95 percent) and therefore increases the likelihood of a hangover. Clear liquors like vodka, rum and gin are better bets than dark or sweet liquors like bourbon, scotch or tequila because they have fewer congeners. Generally, cheaper liquor will result in a worse hangover than more expensive liquor.

After Drinking

Before Bed

  • Take two aspirin with a full glass of water - The prostaglandin inhibitors in the aspirin can decrease hangover severity.

In the Morning

  • Take two more aspirin with a full glass of water - This has been shown to minimize headaches as well as decrease inflammation from leftover prostaglandin.
  • Take another multivitamin - Replenishing C and B vitamins in particular can help get rid of the rest of the toxins.
  • Eat breakfast - A meal that includes eggs (for the cysteine), a banana (for the potassium, and fruit juice (for the fructose) or a sports drink (for the electrolytes, sugars and salts) can get the body on the road to recovery. Keep in mind that caffeinated coffee, tea and soda will further dehydrate a drinker.

For more information on hangovers, alcohol and related topics, check out the links on the next page.