Why is coffee bad for kids?

Coffee can be bad for kids if consumed in excessive amounts because of the caffeine in it, according to KidsHealth and How Stuff Works. KidsHealth says a child needs a small amount of caffeine to experience side effects, which include concentration and sleeping problems and increases in blood pressure.

Children may feel the effects of caffeine for up to six hours, according to KidsHealth. Children who keep drinking coffee and other caffeine sources develop a tolerance and need more to get the same effects they used to. Kids who withdraw from caffeine dependency may get headaches and become irritable. Moderation is critical with coffee consumption.