Reaching for a mug of coffee may be the worst thing you can do to try to sober up, a study suggests.
Coffee can cloud your judgement when you've drunk alcohol, tests found
Research on mice indicates the drink may make you feel that you are coming to your senses - but it is only an illusion.
In fact, it makes it harder for people to realise they are under the influence of alcohol.
The study, by Temple University in Philadelphia, appears in the journal Behavioural Neuroscience.
Lead researcher Dr Thomas Gould said: "The myth about coffee's sobering powers is particularly important to debunk because the co-use of caffeine and alcohol could actually lead to poor decisions with disastrous outcomes.
"People who feel tired and intoxicated after consuming alcohol may be more likely to acknowledge that they are drunk.
"Conversely, people who have consumed both alcohol and caffeine may feel awake and competent enough to handle potentially-harmful situations, such as driving while intoxicated or placing themselves in dangerous social situations."
The researchers tested how well adult mice were able to navigate their way round a maze to avoid unpleasant stimuli, such as bright lights and loud noises.
The animals were given doses of alcohol and caffeine in various combination, and their performance on the maze was compared to others who were given a neutral saline solution.
Alcohol made the animals more relaxed, but less able to avoid the unpleasant shocks.
Animals given caffeine were little better at navigating around the maze, but were more alert and uptight.
In combination alcohol and caffeine appeared to produce relatively alert, relaxed animals that were still incompetent at sidestepping nasty shocks.
The researchers believe that in humans the combination is likely to make people feel that they are not drunk, when in fact they still are.
The doses of caffeine given to the mice were up to the human equivalent of eight cups of coffee.
Dr Gould said: "The bottom line is that, despite the appeal of being able to stay up all night and drink, all evidence points to serious risks associated with caffeine-alcohol combinations."