Due to pain
For intense pain, you would have to work with the source. Often if there isn't an injury, pH imbalances are the main cause of inflammation and pain. To learn more about this please read this acidosis/alkalinity article. ---> pH imbalance.
Mild pain and discomfort often respond to 500 mg of Calcium/Magnesium in a 1:1 balance--just like the old folk remedy of warm milk at night, without the mucus.