Bumps that go away when you bump your head and others donâ€™t has to do with the severity of the damage to the underlying tissue. When you bump your head, you get a bruise because you break small blood vessels under the skin and the blood pools causing discoloration and swelling in the surrounding tissue. As the blood clot (hematoma) breaks down it gets reabsorbed and disappears. If you whack your head hard enough you could damge the skull, the bone may be injured but not broken. You can hurt your skull without causing a fracture. As the bone heals, it could get thicker in the damaged area. The same way your skin might form a scar. You could wind up with a knot that doesnâ€™t go away.
Bumps on the head, even large ones, donâ€™t always warrant a trip to the ER or even a call to your doctor. However a hard hit may shake up the brain â€“ called a concussion, also blood can slowly leak out from a damaged blood vessel beneath the skull, called a hematoma–that push into the brain tissue. Larger hematomas can push into the brain tissue. This can either happen very quickly within an hour, or it can take two or three days. This is an emergency and requires a CAT scan of the head to diagnose. Remember, considering the many times children hit their head, injury to the brain is unusual. Most bumps on the head, even large ones, are not serious.
Loss of consciousness. If your child blacks out, even for a few seconds, this can mean that the force of the bump was strong enough to cause a hematoma. A reassuring sign is that you either hear or see your child start to cry immediately after the bump. This means he did not lose consciousness. If your child is unconscious, but breathing and pink (no blue lips), lay her on a flat surface and call emergency medical services. If you have cause to suspect a neck injury, donâ€™t move the child but let the trained experts in neck injuries transport her.