Sometimes, a cartoon kid might get a boil because of an injury or scratch that got infected. Or maybe they were exposed to something that irritated their skin.
Maybe it's for creating a mysterious or symbolic effect. Sometimes, no face can make the character more enigmatic and leave more to the imagination of the viewer.
Maybe the kid is in a hurry to get home for dinner or to watch a favorite TV show.
Maybe the kid is looking at something behind them that caught their attention.
Maybe it's a unique character design choice to make the kid stand out or give them a mysterious look.
Maybe it's part of a magical adventure or a fantasy plot. The jewel could give the kid special powers or lead to an exciting quest.
It could be that he's been sick and not getting enough rest. Or perhaps he's under a lot of stress from school or family.
The reason could be to bring attention to the need for better understanding and support for those with seizures. It might also be part of a story to show how a character overcomes difficulties related to their health condition.
Perhaps the kid is trying to tell the mother something exciting that happened or to give her a hug. It might also be that the kid wants to share a discovery or a new idea with the mother.
It could be that he's been studying really hard and not getting enough sleep. Stress from schoolwork might be the cause.
Maybe the kid had too much energy or was too excited to sleep. Or perhaps the environment wasn't quiet enough.