When my partner and I stayed with a friend in Rome, I inadvertently locked us all out of his flat on a Sunday night and we had to camp out with a friend.
Gallantly, our friend, surveying the male midday shadows, said it was considered chic to be unshaven on a Monday because all the barbers'shops are shut.
But you are not in Rome, so do not do as the Romans do. If you are a nonbearded man and you have spent the night in a strange bed - or no bed at all - treat yourself to a Bic before bearding the office.
And while you are in the chemist, invest in:
a toothbrush and some toothpaste;
some Resolve if it was that kind of night; and lagain, if it was that kind of night, some vitamin C, but not the fizzy sort as your colleagues do not want to share your lager-sodden burps.
And dig deep to treat yourself to a new T-shirt in an effort to look respectable.
But if you still do not think you can make it through the day without falling asleep at your desk or spending several hours in the lavatory, you should ring in sick. A strategic migraine is better than letting your colleagues see you as irresponsible and unreliable.
Of course, if you have been up all night working on that vital project for a deadline, different rules apply. The more dishevelled the better - what you are seeking now is a mixture of sympathy and admiration.