As urban legends go, the one about unsuspecting trick-or-treaters having their Halloween loot spiked with razor blades is pretty chilling. Spookier still is the "fact" that the only records of serious injury resulting from poisoned booty involved children booby-trapping the items themselves, or parents poisoning their own offspring. I suspect those rumours, like the one about hospitals offering to X-ray trick-or-treat sweets, are also the stuff of legend – but none the less it's enough to put us paranoid parents off altogether. And yet my children have been at near coma-inducing levels of excitement about their plans for weeks. Their outfits are ready, so too their plastic pumpkin buckets, and their last words before falling asleep each night are a variation of "How many more sleeps now, Mama?"

This is one of those classic parenting moments in which I theoretically adhere to one school of thought while practising another entirely. Some people call that hypocrisy; I prefer to think of it as the inbuilt survival instinct of a parent. Because, come tea-time today, I will be watching from a safe distance (about two feet) while my sons, aged three and four and a half, knock on the doors of our neighbours in a thinly-veiled attempt to beg strangers for items that are usually contraband except for on Fridays, special occasions, or when Mama needs to meet an urgent deadline. You see? It makes no sense. I spend all year instructing them never to talk to strangers but, for one night only, I'll actively encourage them to dress up as flesh-eating zombies and demand sugar-laden treats from people they don't know. Why?

Well, why not? I've heard all the arguments against trick-or-treating, from legitimate safety concerns, to the idea that it's just plain rude to let children knock on doors to demand treats. But I've still yet to hear an argument that counters the wonderment and excited glee that trick-or-treating elicits.

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I wouldn't have considered trick-or-treating before we moved to a sleepy coastal town in Northern Ireland. In London we were unlikely to knock on a neighbour's door except to ask them to turn the music down but here, Halloween is huge and it seems churlish not to join in the fun, which culminates with a street parade and a fireworks display over the harbour. It surprised me to learn that Halloween originated in Ireland, and only became big in America in the mid-19th century when the potato famine drove more than one million Irish immigrants across the water. So it's not just a tacky US import after all, and we get to indulge in trick-or-treating in the name of embracing our Irish cultural heritage.

Halloween, or All Hallows Eve, is said to have its roots in the Celtic festival of Samhain, a celebration of the end of the harvest season in Gaelic culture, sometimes regarded as the Celtic New Year. The tradition of trick-or-treating is an adaptation of the medieval practice of souling, where people would offer to sing and say prayers for the dead in return for food. In recent times the "trick" element has made headlines, with feverish talk of knife-wielding hooligans using the opportunity to terrorise the elderly and vulnerable, and rumours that some London boroughs had attempted to ban trick-or-treating altogether. That is precisely why I'm inclined to indulge my little zombies in their Halloween excitement. If we're too afraid of our own shadows to exchange pleasantries with our neighbours, then something's up with society.

Trick-or-treating might afford my children a unique opportunity to understand giving, sharing and neighbourliness. The best maths lesson I've ever had? Dividing up the Halloween spoils with my brother and our cousins. Far from banging on doors rudely demanding treats, trick-or-treating strikes me as a jolly good excuse to strike up conversations with the strangers we live next door to.

What's more, it's good for the economy. Halloween is now a multi-million pound industry in the UK, with some retailers seeing 31 October emerging as the second most lucrative trading period of the year after Christmas (and overtaking Easter, too). Last year, sales of Halloween items, including costumes, themed food and drink, sweets and decorations, were expected to top £195m, rising from an estimated £12m in 2001. According to analysts, British Halloween spending is catching up with the US, where an average family spends approximately £65 on Halloween paraphernalia in a nationwide industry said to be worth £4.7 billion.

While the economic downturn has sunk its teeth into UK spending, Halloween is biting back. Not even a recession can dampen Halloween spirit, it seems. A leading UK Halloween fancy dress and party manufacturer ( smiffys.com) says more customers than ever have placed their orders early this year, with an increase of 124 per cent in the amount spent by customers by May of this year, compared to the same time in 2008. "Over the three months that we ship the Halloween stock to our retailers – August, September and October – we have seen a 15 per cent increase in sales compared to last year, and we expect this figure to grow by the end of the month," reports Smiffy's spokeswoman, Anouska Sawyer. "During this three-month period we've sold just under 124,000 Halloween costumes (that's 206 every hour) and 33,975 units of our white face paint (that's nearly one every minute). Recession? What recession!"

That's a view shared by many retailers, including Pure Party, part of the Clinton Cards group, which has more than 40 stores around the UK and has just launched an online shop to coincide with Halloween ( purepartyonline.co.uk). Pure Party saw a 41 per cent increase in sales of Halloween home decoration packs, and attributes this partly to the fact that Halloween falls on a Saturday this year, which may have prompted more people to host Halloween parties at home.

Kim Einhorn of the party planning company Theme Traders ( themetraders.co.uk) agrees that the recession has had an impact on Halloween spending. "Companies don't want to pay for full Halloween party planning and installation services this year but they're doing it themselves, imaginatively. We're hiring out far more props than ever before – everything from life-size Dracula statues to tables that resemble coffins," she says. "Recession sparks an appetite in people for an escape to a fantasy world, and that's what Halloween is all about."

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Ashvina Lockmum, buyer of false eyelashes for high-street beauty retailer Superdrug, agrees. "Lashes are big business. Brits now spend over £10m a year on boosting their lashes with falsies," she reports. Superdrug expects to sell around 50,000 pairs of false eyelashes during Halloween week.

If Halloween gives consumers an opportunity to escape their recessionary woes, it's also a chance to indulge a dark sense of humour in dark times. According to retailers in the UK and the US, Michael Jackson and the convicted Ponzi fraudster Bernard Madoff are among the most popular costume choices for 2009. Analysts IBIS World report that last year, when the financial outlook was much bleaker, the Halloween spirit remained unaffected and US sales grew 5.1 per cent from 2007.

Liverpool's Alma de Cuba is a former church converted into a bar and restaurant which hosts one of the most popular Halloween events in the country. Last year's event attracted more than 500 revellers and this year's party theme is the "Battle of Angels and Demons". Marketing director Tekla Simo (who fittingly hails from Transylvania, the home of Dracula) says: "We're increasingly seeing people make a huge effort at Halloween to dress up and hit the town, which is very positive for the economy."

Greggs, the UK bakery retailer, took the Halloween spirit a step further this year by inviting a local coven of witches into its new £16.5m bakery in Manchester. Amethyst, Amber and Aquamarine blessed the recipes for a range of Halloween treats including bat biscuits, toffee apple lattices and creepy cupcakes before they were dispatched to 1,400 outlets across the UK. "We were delighted to be invited by Greggs to cast a positive blessing on the bakery and the goodies they're making," says Amethyst. "The traditional blessing we use brings protection and prosperity during an important and ancient British festival and it's great to think we're passing on some positivity to Greggs' customers around the country and at the same time dispelling some of the myths and stereotypes that surround our Craft."

That's a controversial move, given that Halloween is also traditionally connected to the Christian celebration of All Saints; a link that has largely been swept aside by growing commercial influences. In recent years the Bishop of Bolton, the Right Rev David Gillett, has challenged supermarkets to offer alternatives to the scary masks and costumes that are on sale. Halloween Choice ( halloweenchoice.org) exists in partnership with The Children's Society and the Church of England and campaigns for retailers to offer a wider range of goods to mark the occasion. A spokesman said: "Our concern is not with the fact that people are making money out of the event, as clearly the celebration has a positive impact on the UK economy, but with the type of products being stocked and the emphasis on goods designed to scare and shock. Not everyone want to see children dressed as monsters and murderers."

It turns out that flesh-eating zombies aren't actually all that popular with little boys either, so we've compromised on Spiderman costumes this year. Much less scary – and somehow so much more in keeping with the spirit in which we're going trick-or-treating. Where's the harm in a neighbourly visit from a pint-sized Spidey-duo on a dark and wintry night? And I promise to eat the lion's share of the sweets too, just to spare them the evils of the sugar, of course.