When that taste of triple-chocolate brownie sets off the nerves, the nerves respond by causing the blood vessels in the head to swell up. This quick swelling of the blood vessels is what causes your head to pound and hurt. Anything that's very cold, like ice pops, slushy frozen drinks, and even cold soda, water, milk, or juice can make the blood vessels swell. This kind of headache almost never lasts more than 5 minutes, and it goes away on its own. And although you may feel pain , it's not dangerous and doesn't mean that anything is wrong in your body.
Some doctors say that simply eating cold foods more slowly can help prevent brain freeze.
You can also try warming foods up a tiny bit in the front of your mouth before swallowing them. But if you just can't eat that banana split slowly and start to feel a headache coming on, you may be able to slow it down by holding your tongue against your palate. This will warm up your palate a little and you'll be ready for your next bite of banana split in no time. For specific medical advice, diagnoses, and treatment, consult your doctor.