How old do you have to be to buy a lighter in Illinois?

It depends where and what kind of lighter; for instance, if you want to buy a Bic lighter, then really it's the seller's choice. If it's a gas station, they'll probably sell you one. But if you want a Zippo and gas stations don't sell them, then you'll have to go to Walgreens, a smoke shop, or somewhere else, and at those places, you will have to be 18.