What is the most common cause of seizures in children under 3 years old?

The most common cause of seizures in children under 3 years old is febrile illness. This is primarily due to the natural physiological response of young children to fever, which can lead to febrile seizures. These seizures often occur in the context of a rapid rise in body temperature, typically associated with common childhood infections such as viral illnesses.

The prevalence of febrile seizures in this age group is significantly higher compared to other potential causes. While conditions like hypoglycemia, head injury, and epilepsy also can lead to seizures, they are less frequently observed as the primary triggers in infants and toddlers. Hypoglycemia, for instance, can cause seizures but is less common in this age range, especially in a healthy child. Similarly, head injuries are relatively rare in very young children compared to febrile illnesses. Epilepsy is also less common in very young children compared to the incidence of seizures related to fevers. Therefore, febrile illness stands out as the key cause, making it crucial for parents and caregivers to monitor fever and associated symptoms carefully in young children.