In some cases blueberries can cause a diaper rash in children who have a sensitivity to this food. There is a difference though between a food allergy and sensitivity. Usually when a person is sensitive to a certain type of food, it presents as a mild skin irritation. Although this is often times mistaken for an allergy, that is not the case.
While some people are in fact allergic to blueberries along with other fruits, sometimes it is nothing more than a sensitivity. If you know that your child is sensitive to blueberries or any other food, you should avoid giving it to them or try to moderate how much you give them.