I am not a scientist, so I will just copy and paste what WebMD explains about period cramps as below:
Menstrual cramps are caused by contractions in the uterus, which is a muscle. The uterus, the hollow, pear-shaped organ where a baby grows, contracts throughout a woman's menstrual cycle. If the uterus contracts too strongly, it can press against nearby blood vessels, cutting off the supply of oxygen to the muscle tissue of the uterus. Pain results when part of a muscle briefly loses its supply of oxygen.When I suffer period cramp pain, at its server time, I just could not do anything, and it can last up to hours. That pain can waking u you in middle of night and sweating with a pale face.. Sign.. When I touch my belly area in these bad times, its temperature is much lower than the other part of my body. I guess it s due to lack of oxygen and bad flood flow around my uterus area.
Here is some remedies which always work for me:
1. Brown Sugar Hot Drink
This ancient Chinese remedy has been in use for time immemorial. I am pretty sure my mom taught me this remedy and it works really well. Stir the brown in a cup full of hot water. You can add some crushed ginger too. This drink would warm your body up instantly and it would calm the uterus contracts. In china, brown sugar is called :红糖. It has been used in many oriental remedies. If you could not find brown sugar, Hot chocolate drink works just fine too.
2. Put a hot towel or a heated pad on your abdomen.
Again what my mom taught me and works magically. back then, there is no heated pad, I would just damp the towel into very hot water , twist the water out then put the dampen hot towel on my abdomen...In a few minutes, the pain would be reduced. Or search "self heated adhesive pad".. When it is cold, blood wont be able to flow well. that's why squeeze the coldness out of your abdomen is the key.
Try to press these body points, marked in red, will reduce the pain. Gently but with pressure. 5 to 10 mins would be good.
4.Avoid Cold/Strong flavor food. Includes Coffee and Alcohol
These strong flavored food (salty/spicy will pull out water from your body, which make the pain worse for you. Same reason for not drinking coffee or alcohol. Eating or Drinking cold food will impact the blood flowing negatively, which will give you more pain and temporary stop the bad blood flow out of your body.
Before your period, you can try some herb syrup to help the cycle go smoothly.
Chinese motherwort Syrup. Again a ancient still popular Chinese remedy. These syrup is hard to make it by yourself, esp if you are not living in China. In U.S.A, these Chinese herb medicine store would have it.. ask for 益母草膏。
After period, well, as we know, we lost some blood. although our body would generate blood itself, it is good to eat some food help enrich the blood generation.
The most famous/popular herb food Chinese would use is : 四物汤. 4 Herb Soup.