- Read the labels.
Just because someone tells you that an item that they are serving is vegan, that does not mean that they fully understand what vegan means. Things like lactic acid, honey, and other crazy non vegan ingredients tend to hide in seemingly vegan foods. If bags or boxes are lying around, you can casually check them, or ask if they have them for you to check. After all, some people think that fish is vegan.
You just never know what is in something that you haven’t prepared yourself, and you could save yourself an upset stomach. If you feel odd asking, you can always just eat what you’ve brought.
Another note along those lines is to check out what popular mainstream candies are vegan ahead of time. PETA has a great list on their website. One final note about reading labels is not to limit it to food items. Many Halloween makeup products contain beeswax and animal fats. If you can’t find something vegan friendly in your local costume or Halloween store, Amazon has some cheap options.