Approximately 70% of migraine sufferers experience vomiting as part of their migraine attacks. In fact, childhood migraines can involve only nausea and sickness; with no head pain at all. It may sound strange, but of the migraine sufferers who vomit as part of their migraine attacks, many find that they feel better after vomiting. Why is this?
There isn’t a lot of research into this aspect of migraine pain relief, but of what there is, a review paper from 2013 summarises some possible reasons why vomiting can bring migraine headache relief.
One theory is that being sick triggers the release of chemicals which ease pain within the body. This theory is supported by a study from 1986 which suggested that vomiting triggers the release of endogenous opioids – these being endorphins which ease feelings of pain.
Another theory is that throwing up could somehow interact with the vagus nerve of the parasympathetic nervous system in a way that relieves pain. Vagus nerve stimulation, as well as being able to induce vomiting, can also relieve migraine headache pain, and some doctors now use vagus nerve stimulation implants to relieve pain in those sufferers who experience chronic migraine headaches.
Two more theories are that vomiting may change the blood flow in the body in such a way that pain or inflammation is reduced, or that, since vomiting happens towards the end of a migraine attack, it may simply be the beginning of the reduction of migraine symptoms.