It really depends on the child and their understanding about money. No one knows better than you what your child is capable of especially when it comes to spending money and becoming apart of the consumerism public.
But they should at least know how to count. I also encourage that you give them some responsibilities along with handing out money, a gift is one thing, earning the money is another.
Another good thing is to give them some guidance on how to spend their money. Some kids are instinctively better about money than others but it is a learned concept, teaching a budget/saving concept is also invaluable.
But you know best and you can help them a lot when you teach them as soon as possible how to use money well. Allowances are good for that reason.