"Ice cream headaches" result from quickly eating or drinking very cold substances. It is commonly experienced when applying ice-cream (or similar) to the roof of the mouth (palate) or when swallowing it. Typically the headache appears in about 10 seconds and lasts about 20 seconds although some people experience much longer lapses of pain, with the pain seeming to relate to the same side of the head as the cold substance was applied to the palate, or to both sides of the head in the case of swallowing. The most effective way to prevent it is to consume the cold food or liquid at a slower rate. Keeping it in one's mouth long enough for the palate to become used to the temperature is also an effective preventative.
Ice cream headache is the direct result of the rapid cooling and rewarming of the capillaries in the sinuses. A similar but painless blood vessel response causes the face to appear "flushed" after being outside on a cold day. In both instances, the cold temperature causes the capillaries in the sinuses to constrict and then experience extreme rebound dilation as they warm up again.
In the palate, this dilation is sensed by nearby pain receptors, which then send signals back to the brain via the trigeminal nerve, one of the major nerves of the facial area. This nerve also senses facial pain, so as the nerval signals are conducted the brain interprets the pain as coming from the forehead—the same "referred pain" phenomenon seen in heart attacks. Brain-freeze pain may last from a few seconds to a few minutes. Research suggests that the same vascular mechanism and nerve implicated in "brain freeze" cause the aura (sensory disturbance) and pulsatile (throbbing pain) phases of migraines.
It is possible to suffer from an ice-cream headache in both hot and cold climate conditions.