What really causes migraine?

What is migraine? It is a medical term for headache.Some causes related to a common headache are stress due to worry,eyestrain or problem related to astigmatism or any eye related diseases. Most of the common experiences felt by these patients are pains located on one side of the head,glaring light and nausea. They usually lack appetite.They just feel nauseated when food is served. Ice packs are quite a relief or a warm soup could satisfy their hunger.There are lots of drugs placed in the market but are they giving a lot of help?A complete head massage or acupressure or other natural remedies are also giving relief with no side effects.If and when the symptoms persist after the patient tried his/her best,then that is the best time to approach a Medical Expert.