The so called hangover - which many of us have had - well, approximately 80% of drinkers, and despite their often horrendous nature, they don’t seem to put us off doing it again. But why do we actually get them, what is it about drinking too much alcohol that makes you feel like you want to stay in bed under your pillow and eat sweet or fatty foods? So here is some of the science behind the morning after hangover.
A single alcoholic drink is enough to trigger a hangover for some people, while others may drink heavily and escape a hangover entirely. While many are familiar with the delightful symptoms of a hangover (headache, nausea, fatigue, dehydration etc.), science is still researching in to what really causes them.


For many years, dehydration was blamed as the primary cause of hangovers. Alcohol is a diuretic, meaning it makes you urinate more and hence you lose water. It does this by suppressing the body’s anti-diuretic hormone vasopressin, which prevents you from urinating excessively. Also, if you are drinking a large number of cocktails or a large volume of your favourite wine, there is the chance you are probably not drinking much water. And then drinking a litre or two of water the next morning does not instantly fix the hangover.
So, dehydration probably is not responsible for the majority of your hangover, but it might give you a serious headache. These are an unfortunate by-product of your body attempting to restore fluid levels. Your blood vessels narrow, restricting the flow of blood and oxygen to the brain, which then tries to compensate by dilating blood vessels, which can cause swelling. Although the brain itself can not feel pain, the discomfort may result from pain receptors in the lining that surrounds the brain.
Alcohol can irritate your stomach and intestine, causing inflammation of the stomach lining and delayed emptying of your stomach contents. It also causes you to produce more gastric acid alongside increasing the levels of pancreatic and intestinal secretions. Both of these can lead to nausea, or even worse cause you to throw up.
It has been found that a key component to the cause of a hangover is a toxic compound called acetaldehyde, which builds up as a by-product as our body processes alcohol. It is thought to be up to 30 times more toxic than alcohol itself, and has been found to produce hangover-like symptoms in controlled studies.
One study found that hangovers are actually the result of our immune systems. One study found that people with hangovers also had high levels of cytokines, which are substances secreted by immune cells that are involved in inflammation and cellular communication. Normally, these help the body fight off infections, but if you inject large amounts into healthy bodies, they start to experience hangover symptoms like nausea, headache and fatigue. Furthermore, some research results have hinted that abnormally high levels of cytokines could disrupt memory formation in the brain, which could help explain why some wake up totally oblivious of their late night tomfoolery.
A hangover is the consequence of having consumed too much alcohol - and an accumulation of several factors. There can be an inflammatory response by the immune system to alcohol, which may affect your appetite, concentration and also memory. Some people can have their blood sugar levels fall steeply when they consume alcohol, resulting in shaking, mood swings, tiredness, fatigue, general weakness, and even seizures in some severe cases. Alcohol consumption can cause the blood vessels to dilate, which can cause headaches. Although sleeping when drunk is common, the quality of that sleep can be very poor. The individual can wake up even more tired and still sleepy, even groggy.
Congeners, also known as fusil oils, are a by-product of the fermentation process and are responsible for most of the taste and aroma in alcoholic drinks. They are essentially impurities of which there can be hundreds of different types, including the already mentioned acetaldehyde and methanol. In effect, our bodies treat them as a poison, and a headache is a very common symptom. These reactions are likely so complex that they could explain why mixing different types of alcohol can cause a hangover - a greater variety of congeners could lead to a wider variety of effects, as well as a greater need for painkillers the next day.
Because all alcoholic beverages begin with fermentation, any type is likely to have congeners but distillation can remove many of them. It is for this reason that clear spirits (such as Gin or Vodka) tend to produce less intense hangovers than congener-rich alcohol (red wine or cognac). In March 2010, Brown University’s Center for Alcohol and Addiction Studies published research demonstrating how young drinkers who received bourbon to the point of intoxication were in a worse state the following day than their peers who drank vodka to the same point of intoxication.
Alcohol flush reaction as a result of the accumulation of acetaldehyde, the first metabolite of alcohol. After being ingested, ethanol is first converted to acetaldehyde by the enzyme alcohol dehydrogenase and then to acetic acid by oxidation process. By causing an imbalance of the body’s redox system, alcoholic beverages make normal bodily functions more difficult.
Alcohol also induces the CYP2E1 enzyme, which metabolizes ethanol and other substances into more reactive toxins. In particular, in binge drinking the enzyme is activated and plays a role in creating a harmful condition known as oxidative stress which can lead to cell death.
Acetaldehyde is between 10 and 30 times more toxic than alcohol itself and can remain at an elevated level for many hours after initial ethanol consumption. In addition, certain genetic factors can amplify the negative effects of acetaldehyde. For example, some people (predominantly East Asians) have a mutation in their alcohol dehydrogenase gene that makes this enzyme unusually fast at converting ethanol to acetaldehyde. In addition, about half of all East Asians convert acetaldehyde to acetic acid more slowly (via acetaldehyde dehydrogenase), causing a higher build-up of acetaldehyde than normally seen in other groups. The high concentration of acetaldehyde causes the alcohol flush reaction, and since this action is highly uncomfortable and the possibility of a hangover being immediate and severe, people with this gene variant are less likely to become alcoholics.
Whatever the ultimate cause, don’t expect the scientific community to find a silver bullet, a magic, simple remedy or day after cure for all. Drink in moderation, at a controlled pace and with good substantial food, stay well hydrated before the event, before you go to sleep and when you wake up - so you can remember and enjoy all the flavours and moments.