The primary cause of swelling on the head after a fall is the leaking of fluids or blood underneath the scalp from the veins in the scalp, according to KidsHealth. The bump that forms at the sight of a head injury is commonly referred to as a "goose egg" and takes a few days to a week to go away.
A swollen bump on a head from an injury is not normally life-threatening unless it's associated with other symptoms. It's important to contact a medical professional if the patient loses consciousness, repeatedly vomits or is hard to wake up. If swelling is the only symptom from a head injury, it's crucial to monitor the patient for up to 24 hours and apply ice to the affected area to reduce the pain and swelling.