It was the blood-spattered dentist's tunic that brought me up short.

Displayed between Tesco's toiletries and the fruit and veg was a child-sized Hallowe'en outfit. It depicted a hatchet, a pair of pliers and a knife, all dripping red, the splash marks suggesting a frenzy of stabbing, amputation and extractions.

The day before, in another store, a kiddy's surgeon's outfit had also caught my eye, so drenched in gore it could have been wrung out and bottled for the blood bank. Alongside were zombies, aliens and - how terribly tame - sparkly witches' costumes. Then there were the adult outfits, the men's predictably murderous, and the women's skirts shorter than a psychopath's temper or a ballerina's tutu.

When did Hallowe'en change from being a spooky festival to one so grisly it deserves to be X-rated? And where did the tumshies go? Visit any supermarket and you'll be faced with so many shelves of pumpkins you'd begin to think you were in Ohio. They may be prettier than neeps, but as with so many aspects of this once quaint but oddly meaningful occasion, the American imports are a triumph of style - and convenience - over substance.

Carving eyes and a jagged smile out of Scotland's toughest vegetable and turning it into a candle-lit sprite to carry around the streets was not only character forming - it could take days - but a rite of passage whose smell, feel and mood I, and millions like me, will never forget. There was something, also, about the gnarled look of a turnip lantern that captures Scotland as the glamour of an easily-scooped and fresh-faced pumpkin never could.

Hallowe'en was always a big day in Scotland. Marking the end of autumn, it was seen as the night when, with winter approaching, the dead were most likely to drop by.

Robert Burns wrote a rollicking poem about it, describing the antics Ayrshire folk got up to on this dark, eldritch night. Most of their games were designed to predict who one would marry, as when he describes the custom of young men pulling three stalks of oats. If the top of the last straw had no grain then the lass one would wed, he explains, would "come to the marriage bed anything but a maid".

The mood of the evening, Burns suggests, was amusing, not menacing. Even the tradition of guising, intended to throw vengeful ghosts off their victims' track, was tongue-in-cheek. As was, one hopes, the habit of drizzling stale urine around doorways to ward off angry ghosts. Perhaps it was the living they were really trying to repel. For many, though, the thought of the departed returning was not something to be scared of, and food was laid out, and the fire stoked, to make them welcome.

The way Hallowe'en is celebrated today, however, the original elements are all but forgotten. Offering just another slick marketing opportunity, it is becoming as tacky and ersatz and costly as Christmas and Easter. Gone is acknowledging the place the dead still hold for those they have left behind, or of speculating about the future in a playful flirtation with the supernatural.

Also vanished is the once real fear of witches and demons, replaced by the kitsch and grotesque emphasis on man-made violence and savagery. Not to mention a surfeit of sugary treats. Alongside the tasteless Hallowe'en outfits, most shops also sell bumper bags of sweets to dole out to guisers and help reduce their teeth to rubble.

Cynically hijacked to fill the commercial doldrums before Christmas, Hallowe'en has at the same time been refashioned, like so much of our culture, into an American shape. This, despite the fact that when Hallowe'en was first held, America as we know it did not exist.

Just as most of us are probably more familiar with back-street Baltimore or Manhattan than with Inverness or Hawick, we are in danger of allowing American values to swamp us. It's as if we think everything they do is better.

Whether it's language, food or television shows, we seem always to be following in their footsteps and aping the way they behave. We're like children, tottering around in shoes ten sizes too large. Except that in the case of Hallowe'en, in forgetting our ancient traditions, or handing them over without a thought, we are guilty of being not childish but careless.