Alcohol is a mood-altering substance. It affects the nerves that pass messages around the body by slowing them down, and the more you drink the greater the effect. The reason people often get more lively when they’ve had a drink is that alcohol affects parts of the brain responsible for self-control.

Alcohol is eventually metabolized by enzymes in the liver at the rate of about 1 fluid ounce (29 milliliters) per hour, but this process can cause damage to the organ in the long term. Alcohol is also excreted by the kidneys as urine, or breathed out by the lungs. Whole ethanol molecules can even seep from the skin. Of course it can also make a violent exit while vomiting.

Getting drunk occurs when you consume alcohol faster than you can break it down. As you drink, the alcohol passes into your bloodstream. Ethanol is the intoxicating part of alcohol and its molecules are so small that they can pass into the gaps between brain cells. There it can interfere with the neurotransmitters that enable all the brain’s activities.

Severe cases of heavy drinking can result in alcoholic poisoning, coma, or death. Your reactions also slow down, and as you drink more, you may become uncoordinated or unsteady on your feet. Your speech may get slurred and you may start seeing double. If you’ve had a lot to drink you may also experience strong emotional responses - for instance, you may become aggressive or tearful. And because your judgment is impaired, you may do things that you might not normally do from dancing on tables to going home with strangers. They may seem a good idea at the time but can be extremely dangerous.

If you drink fast, alcohol will start to flood the brain. Fortunately, alcohol can give some warning signs as it penetrates the brain and central nervous system, so if you spot the signs in yourself or a friend, moderate your or their drinking or stop drinking further amounts. The last thing you would want is to lose control, vomit, or end up in the hospital.

Women are also thought to have less of the enzyme alcohol dehydrogenase, which breaks down alcohol, so they will get drunk more easily and sometimes You end up dehydrated and that’s a big reason for hangovers.

Let’s look at the physiological effects first. The active component in booze is ethanol, which as molecules go, has all the sly charm of one of those beery lads who can worm his way past the velvet ropes of any bar in the world.