Armfuls of confectionery are a delicious, sugary reward for dressing up as devils and witches to scare the wits out of the neighbours.
But trick-or-treating will become a "Halloween horror" for children unless parents take steps to protect their teeth, warn dentists.
The Royal College of Surgeons has issued tips to ensure rotten smiles are just for Halloween.
Prof Nigel Hunt said: "We don't want to spoil the fun."
But the dean of the faculty of dental surgery said the state of children's teeth was a "national scandal" and added: "We want to help parents make sensible decisions about letting their children eat sweets at Halloween and all year round."
His tips include:
If children are given sweets on Halloween they shouldn't eat them straightaway, but save them to have with a meal at home to reduce the impact on their teeth.
If trick-or-treaters visit you over Halloween, consider giving out alternative treats to sweets such as stickers or balloons.
Limit the number of sweets you give out to each child - think about only giving one or two rather than a whole bag.
If the child is thirsty, make sure they do not have sugary drinks, water is better.
Even though they may be tired, make sure children brush their teeth with fluoride toothpaste before going to bed.
Prof Hunt said: "Celebrating Halloween by trick-or-treating has become very popular in the UK in recent years.
"As a parent myself, I know the delight children take in donning fancy dress and visiting the neighbours to collect as many sweet treats as they can carry.
"Unfortunately, those sweet treats can be a Halloween horror for kids' teeth, sugar is one of the biggest culprits for nasty tooth decay."
Children under the age of 10 have more than 179,000 teeth extracted each year and around a quarter of three-to-five year olds have tooth decay.