Alcohol is the obvious culprit behind a hangover.

But it isn’t always the alcohol itself. Its diuretic or dehydrating effects actually cause most hangover symptoms.

Chemicals called congeners can also cause more intense hangovers.

Read on to learn more about what congeners are, which drinks to avoid, tips for recovery, and more.

Alcohol has a wide range of effects on your body, many of which contribute to hangover symptoms.

Some of these include:

  • Dehydration. Alcohol is a diuretic, which means it makes you pee more often. As such, it’s easier to become dehydrated both during and after drinking. Dehydration is one of the main causes of headaches, dizziness, and, of course, thirst.
  • Gastrointestinal effects. Alcohol causes irritation and increases acid production in your digestive system. Depending on how much you drink, alcohol can also speed up or slow down the passage of food matter through your gastrointestinal tract. These effects are associated with nausea, vomiting, and diarrhea.
  • Electrolyte imbalance. Alcohol intake affects your body’s electrolyte levels. Electrolyte imbalances may contribute to headaches, irritability, and weakness.
  • Immune system effects. Drinking alcohol may impair your immune system. A wide range of hangover symptoms, including nausea, decreased appetite, and inability to concentrate may be related to temporary changes in immune system function caused by alcohol.
  • Low blood sugar (hypoglycemia). Drinking limits the production of sugar (glucose) in the body. Low blood sugar is associated with fatigue, dizziness, and irritability.
  • Dilated blood vessels (vasodilation). When you drink, your blood vessels widen. This effect, known as vasodilation, is associated with headaches.
  • Difficulty sleeping. Although drinking too much can leave you feeling sleepy, it also prevents high-quality sleep, and may cause you to wake up in the night. The next day, you might feel drowsier than usual.

These symptoms vary from person to person and can range in intensity from mild to severe. Sometimes, they’re enough to derail your entire day.

Congeners are chemical by-products of the fermentation process that gives alcoholic drinks their distinctive flavor.

Some common congeners include:

  • methanol
  • tannins
  • acetaldehyde

Congeners are found in higher concentrations in darker drinks, such as:

  • bourbon
  • whiskey
  • red wine

Clear liquors, such as vodka and gin, have comparatively lower concentrations of congeners. In fact, vodka has almost no congeners at all.

Congeners are associated with more severe hangovers.

In a , researchers compared participants’ self-reported hangover severity after drinking bourbon or vodka.

They found that participants tended to report feeling worse after drinking bourbon, which has a higher congener content.

Pro Tip:

The darker the alcohol, the more congeners there are. And the more congeners there are, the more likely you are to develop a hangover. Opt for a light-colored beer or clear liquor.

For some people, as little as one drink can trigger a hangover.

Other people seem to be able to get away with several drinks, or even a night of heavy drinking, without experiencing much in the way of next-day effects.

So, why are certain people more prone to hangovers? A variety of factors may increase your risk.

These include:

  • Personality. Certain personality traits may influence your hangover symptoms. For example, a recent study suggests that people who are shy are more likely to experience anxiety when hung over.
  • Genetic factors. Among people who have a particular genetic variation, as little as one drink can cause flushing, sweating, or even vomiting. Having a family history of alcohol use disorder also affects how your body processes alcohol.
  • Health status. According to a recent study, hangovers were associated with poorer self-reported health status.
  • Age. The results from this 2013 study and this suggest that younger people are more likely to experience more severe hangovers.
  • Sex. Some research suggests that women are more likely to experience hangovers than men.
  • Other behaviors associated with drinking. Smoking cigarettes, using drugs, or staying up later than usual may exacerbate a hangover.

Hangovers tend to go away on their own, usually within 24 hours.

However, the progression and severity of symptoms over time can vary from one person to the next.

A recent study found that most hangovers follow one of three time patterns, and that different hangover patterns are associated with different reported symptoms.

For instance, participants who reported stomach symptoms were more likely to experience a hangover that followed an inverted U-shaped curve, with symptoms peaking around midday and subsiding in the evening.

This suggests that different hangover symptoms may appear and fade at different times.

Time is generally the best cure for a hangover. While you wait it out, you may find that the following tips help take the edge off:

  • Rehydrate. How much water you need to drink when you’re hungover usually depends on how much you drank the night before. As a general rule, fill a large water bottle and take a sip every couple minutes. Keep drinking at a steady pace all day and into the next. You can also try drinking juice, a sports drink, or herbal tea.
  • Eat something. Foods that contain carbs can help stabilize your blood sugar and settle an upset stomach. Start slowly. If you’re feeling nauseous, opt for something plain, like a banana, toast, or crackers.
  • Take an antacid. An over-the-counter (OTC) antacid, such as Alka-Seltzer, Tums, or Pepto-Bismol, may provide relief for an upset stomach. To settle your stomach naturally, try adding a tablespoon of fresh grated ginger to some hot water.
  • Replenish electrolytes. Sodium-rich liquids can help to balance your electrolyte levels, targeting symptoms such as headaches and dizziness. Try sipping soup broth to replenish sodium levels.
  • If necessary, take a pain reliever. For bad headaches, an OTC anti-inflammatory drug should do the trick. Aspirin or ibuprofen (Advil) are recommended over acetaminophen (Tylenol), since acetaminophen can worsen the toxic effects of alcohol in the liver. Follow the dosage instructions on the label.
  • Go back to bed. Hangover symptoms are often worse due to lack of sleep. If you can, try to sleep in longer or take a nap later on in the day. With an extra couple hours of rest, you might find that your symptoms disappear.
  • Consider vitamins and supplements. Vitamins and natural products may help with one or more hangover symptoms. This 2016 review identifies red ginseng, Korean pear, and ginger as potentially effective in treating certain hangover symptoms. Research is limited, though. Talk to a pharmacist or other healthcare professional before taking supplements.

Prevention is the best treatment for a hangover. The next time you plan to drink, try the following:

  • Eat a carb-rich meal. Having a meal rich in carbs, such as brown rice or pasta, can help you slow down the rate that alcohol is absorbed into your bloodstream. This may prevent hangover symptoms the next day.
  • Opt for light-colored drinks. Choose drinks that are clear-colored, which tend to be lower in congeners. Lighter drinks are less likely to lead to severe hangovers.
  • Avoid carbonated drinks. Carbonated or fizzy drinks speed up the rate alcohol is absorbed in your bloodstream, which could contribute to hangover symptoms the next morning.
  • Avoid cigarettes. Smoking affects your hydration, immune system, and sleep quality, leaving you with a more intense hangover.
  • Drink enough water. Drink water steadily throughout the night. Try having a glass between each drink, and another glass before you go to bed.
  • Know your limit. If you know that five or six drinks will result in a hangover, find ways to limit the amount you drink. For example, try alternating between alcohol and non-alcoholic drinks or taking a half-hour break between each drink. Use other activities, such as dancing or socializing, to break up the rounds.
  • Get enough sleep. If you know you’re going to be up late, make time to sleep in.